Figure 1: View from directly standing on the "A"


Sentinel Peak is a 2,897 ft (883 m) peak that can be found in the Tucson Mountains and is located in Tucson, Arizona. The original name of the mountain, which is located just southwest of downtown, was procured from its function as a lookout point for the Spanish. In 1915, fans of the University of Arizona football team whitewashed a large "A" on its side to celebrate a victory, and the tradition has been kept up ever since -- the permanent "A" is in white paint and  was made out of local basalt rock. The Pima village and cultivated fields that once lay at the base of the peak are long gone, although John Warner's 19th-century house at the base still stands. During the day, the peak is a great place to get an overview of the town's layout; at night the city lights below form a dazzling carpet. Getting up to the summit is extremely easy with a road that takes you straight up the mountain and also loops around. There is a small path from the overlook near the painted A on the mountain that you can take to reach the summit. There is also the Sentinel Peak trail which you can take to A Mountain as well as to the side trail-head up Tumamoc Hill.  The peak is also part of a 272 acre park, which is the largest natural resource park in the City of Tucson. 

History of Sentinel Peak

Prior to the name it holds today, this historical landmark held many different titles through the years. One of the first titles this peak held was Picket Post Butte because of it's use as a sentry station during the Civil War. Soldiers were posted there in "fort like" constructs and the station was used to warn of approaching enemies, such as raiding Apaches, and often times a canvas was stretched over the top to reduce some of the harsh Arizona sun rays. Centuries ago the area was plentiful with green plant life and a Native American tribe, The O’odham people once utilized these plants for food and other uses. They called the mountain Chuk Son, which referred to their village at the base. When the Spanish began colonizing the area, they gave the O’odham the name, “Pima”,  Warner Mill also used to be located at the base of the peak and thus was also sometimes referred to as Warner's Mountain. The base has been home to Indian tribes, Warner Mills, and the community even today continues to decide how to use the space to its biggest advantage. In 2018, there were two majors proposals on the use for the base, one being Tucson Origins Heritage Park and the other being The Sonoran Desert Park Plan. 

For more information on both proposals, click here


Approximately 30 million years ago, the Santa Catalina mountains experienced a volcanic intrusion through ancient granites. This event led to the deposition of volcanic rock such as basalt and rhyolite. 5 million years later, this rock deposit (which will eventually become the Tucson Mountains )moved west as the Catalina detachment fault spread the two rock formations apart from each other. Over time (12 to 6 million years ago), this separation allowed the Tucson basin to fill with the eroded sediments from the Catalina and Tucson mountains. It is speculated that since volcanic rocks tend to contain calcium rich plagioclase feldspar, the soils in the Tucson basin harden and form caliche. While Sentinel peak is part of the the Tucson mountains, the peak its self is not a retired volcano despite popular belief.

According to WryHeat by Jonathan DuHamel, the mountain is composed of volcanic rocks, called igneous rock, that have a conical shape with a low area in the middle leading some people to think it was a volcano. however, the hills are really an erosional remnant of volcanic flows about 20 - 30 million years old which once extended west to the Tucson Mountains and east into the valley towards downtown Tucson. 

The layers of rock at the Sentinel Peak is a basaltic andesite which dates back to 23-24 Ma. The cap is a 30-36 meter thick layer of tuff, which is volcanic ash, piled onto each other.

Further proof that Sentinel Peak or "A Mountain" was created by a once active volcanic field is that there is volcanic ash and breccia, and ancient lava beds found on the mountain. What was once an active volcanic field has turned into an area that is plentiful of different minerals and Saguaro. The Santa Cruz river use to lie just east of the mountain, however it now runs underground. There is a ridge that can also be found near the underground river that was used to allows water to be exposed to the surface. The mountain is plentiful with Basalt rock, which has been used to construct some homes in Tucson as wells as various walls of the University of Arizona campus.

Source: AZGS

Etymology of "Sentinel Peak"

By 1883, the remains are all the still existed of the fortification originally on this peak. These remains included "A circular wall, about 3 feet thick and made of boulders, [that] enclosed an area about 8 feet in diameter. North of the circular structure was a small wall, roughly two feet high and about 10 feet long. To the east were traces of another, smaller circular wall." This was known as the remains of Sentinel station it was called this because a sentinel or guard would be stationed there to watch out for any enemies that would approach to attack. The stone fortification was placed there to originally protect the guards who were posted there, during the Civil War, from sun.

In 1925, there were still traces of these remains, but it wasn't noted as to what was really left there at the top of the peak. 

History of the ‘A’

Positioned right next to the Santa Cruz river, Sentinel peak provided a strategic lookout as crops were often grown in the floodplains at the base of the mountain. This location is known as Tucson's original birth place. Original inhabitants utilized the peak to be able to see signal fires until 1692. After this, it was repurposed by Spanish settlers (mostly known as Father Kino and his group). It wasn't long until Tucson was founded as a city in 1775. Originally owned by Mexico, Tucson and a lot of other land was acquired by the United States in 1853. This transaction was known as the Gadsden purchase (which was 10 million dollars) and was the conclusion of the Mexican-American war. 

On February 14th of 1912, Arizona became the 48th state with Tucson being the oldest city. It was not long after that Sentinel Peak became "A Mountain" in 1914. This happened when University of Arizona students created and constructed the 'A' out of black basalt rock; hence the new name A Mountain. The idea struck to make the 'A' after a previous star football player, Albert Condon, convinced one of his civil engineering professors to make this monument a class project to celebrate their winning game of 7-3 over Pomona College on Thanksgiving Day. Condon also came up with the idea of making an “A” on the mountain after he noticed Pomona College had a “P” on their hillside.   After cleaning out all of the plants and cacti around the area that they were going to build the 'A', the class was then able to get to work on creating the 'A'.  The class went up to Sentinel Peak every Saturday to work on this task of creating the 'A'. The class first cleared the site of cacti and shrubs, then hand dug trenches for the foundation.    The 'A' was finally finished after two years of work and was then painted white.  The 'A' was required to be painted white by the city of Tucson. The “A” wasn’t painted until October 23, 1915, when the football team and fans decided to paint it after the football team won a game against Cal State Pomona. The cost to create the 'A' was $397, the A is 70 ft wide and 160 ft long and just around 5 ft thick. 

An article in the Arizona Daily Star by David Leighton dives deep into the tales of "A" Mountain which includes murder, adultery, and dirty deals. As Leighton notes in his piece, many Tucsonians at the time had no idea that the land was eventually privately owned, by Jim Dodson, for real estate purposes: "In 1922, Jim’s curiosity about the possibilities of Sentinel Peak turned to action when he filed a stone-and-timber claim — a cheap way to acquire land deemed unfit for farming — on 160 acres. The following year his wife filed her own claim on 40 acres, which included the "A" built by students of the university and completed in 1916. Both claims were approved by the state land office in 1924, and much of "A" Mountain fell into the hands of private owners — although almost no Tucsonans knew it. In the end, the couple owned 200 of the 272 acres that comprise the current Sentinel Peak Park." (David Leighton for the Arizona Daily Star)

In 1925, during the dispute for the land, Dodson agreed to give the city of Tucson 20 acres of the land on Sentinel Peak for the park they wanted to create; along with the 5 acres already given for the ‘A’. The dispute was difficult because the lawyers Dodson had was also the attorney for the City of Tucson, thus making it so the city had to hire attorney’s from Phoenix.


What the ‘A’ is used for & Hiking the 'A'

Not only is A Mountain a pretty sight to look at but visitors, locals, and students all have the opportunity to drive, bike, or hike up the mountain. The mountain offers trails that are available to hike. One of the trails that is available for people to hike is known as Gilbert Escandón Jiménez trail, formerly known as the Sentinel Ridge Trail. It was renamed for Jiménez because he used to help with the upkeep of the trail and hiked the trail for more than 70 years. The trail is 2.5 mile round trip and does not reach the tip of the peak.  This is a popular tourist site when visiting Tucson because of the history behind 'A' mountain. Many use this destination as a lookout point to look at the city of Tucson.  Standing at the bottom of 'A' mountain allows for breathtaking views of Tucson during sunrise and sunset.  This mountain is a reminder that the University of Arizona is steeped on pride and tradition. Below are some links to different trails and hikes you can visit.

While these hikes are short, they also connect to other trails that take hikers all throughout the Tucson mountains. Here you can find other old structures such as "Stone house", which was originally a ranch house built in 1930. 



The majority of the time the color of the ‘A’ on Sentinel peak is painted white.  The ‘A’ stays white in respect to the tradition of the ‘A’, which was required to be white by the city when it was made. However, there are times where the ‘A’ is painted different colors to represent things going on in the world or the community. Every year for St. Patrick's day the ‘A’ on the mountain is painted green, a tradition that started in 1993. When the war with Iraq was started and many people disagreed with the war, the ‘A’ was painted black. The ‘A’ was painted red, white, and blue in April of 2003 to show support of our troops, but also to show patriotism. The students from Arizona State University (ASU), the University of Arizona’s rival, sometimes will paint the ‘A’ in their colors on the week of the UArizona VS. ASU; territorial cup game. 

As recently as March of this year, 2020, the 'A' on the mountain was painted blue too honor healthcare workers who were on the frontlines during the COVID-19 pandemic. 

Source: KGUN 9 on Your Side


History of ‘A’ Mountain importance to University of Arizona

‘A’ Mountain is a huge staple to the community of Tucson and the University of Arizona. As the mountain got that nickname due to traditions created by the university. For homecoming, every year incoming freshman are able to go paint the ‘A’ before the game. This year, 2020, marks the 96th year of this tradition; which is known as ‘A’ day and sponsored by the community of Tucson and The Blue Key National Honorary. Another tradition UArizona has every year at homecoming is the lighting of the ‘A’, which always kicks off the start of Homecoming week. Students, Alumni, and facility gather at Main Gate Square where they sing Bear Down with the UArizona band and cheerleaders while the ‘A’ is being lit by the Bobcats Senior Honorary. This tradition has been going on for over 100 years and has been upheld by the University of Arizona Alumni Association, which has ignited this tradition through many generations of Wildcats.

To check out the lighting of the 'A' mountain click here.

To members of UArizona, this mountain represents everything that is "Wildcat Country". This mountain represents the pride and tradition of the University of Arizona as well as the historic events and people that have in some cases even called the mountain home. 

Importance to the local community

Aside from being a look out for past inhabitants, the land at the base of the mountain and alongside the Santa Cruz river provided ideal conditions for cultivating crops. As of 2003, the Kino Heritage project has been determined to develop land in an effort to bring back vegetation that original Spanish settlers (Father Kino and the Franciscans) grew. 

A Mountain is a very important landmark to the community of Tucson and the community of the University of Arizona. The mountain is a popular spot amongst community members because of its novice hiking trail, and breathtaking views. All of Tucson can be seen from its peak, including the University of Arizona, downtown, and Mount Lemmon. 

According to, the park received a $320,000 set of improvements including new trails and park entry signs, two new handicapped-accessible parking spaces, two shaded plazas and a paved path connecting the improvements. Furthermore, The trail improvements and other projects in this upgrade were done with the community in mind, according to Councilwoman Regina Romero. The trails are also "ADA accessible," she said, meaning that they meet Americans for Disabilities Act standards for handicapped access.


Source: Wikipedia

The lighting of ‘A’ Mountain

The annual lighting of the ‘A’ is tradition to the University of Arizona that kicks off the start of Homecoming week. The Bobcats Senior Honorary lights the mountain and allows students, alumni, and faculty to join in on the festivities at Main Gate while singing bear down with the band and cheerleaders while the ‘A’ is being lit. The ‘A’ glows red over Tucson to signify that homecoming week has begun. This tradition has been upheld by the University of Arizona Alumni Association, which has ignited tradition throughout many generations of wildcats.  This tradition of lighting the 'A' has been going on for over 100 years.  

To check out the lighting of the 'A' mountain click here 

Details about the ‘A’ and the mountain

The ‘A’ on A Mountain stands proud and tall at a whopping 160 feet by 70 feet wide. The mountain itself is 2,901 feet looking over the main area of the city that is West of Tucson. This landmark is easy to spot in the heart of the city, making it a focus to the Tucson community and the University of Arizona. It is one of the many beautiful and historic monuments that Tucson has to offer. The views from the top are incredible and an amazing way to really see all of Tucson.

According to the Center for English as a Second Language, Sentinel Peak is where Tucson gets its name from. In the Tohono O'odham language the word Cuk Ṣon means "[at the] base of the black [hill]". From that word, we get the now common form "Tucson". Sentinel Peak is the "black hill" referred to in the original Tohono O'odham language. 


Figure 3: View of the "A" before the repainting (Arizona Daily Star)

Figure 4: Aerial photo of Sentinel Peak (Zach Malmgrem)


 Environmental Threats

While A Mountain is well known for its exceptional city views and key lookout points, visitors unknowingly come to notice the elements of destruction that are present upon the environment as well. Most evident being the multiple areas of vandalism- a plethora of broken glass and bottles, a gazebo covered in spray painted calligraphy, an array of cigarette butts and even more trash. The human impact permitted on this popular local and tourist check-in spot has resulted in a need for cautionary action, so much so that the Tucson City Council of Action deliberately put together a plan in order to restore the attributes of Sentinel Peak. Beyond the widespread of vandalism found throughout the mountain trails, the Tucson City Council along with the Tucson Parks and Recreation staff are implementing techniques to control and stabilize this environment. The deterioration of habitat, erosion, spread of invasive species, and loss of vegetation are significant problems that are slowly effected the condition of this area. The impact of humans, climate conditions, and a lack of water resources have all contributed to the overwhelming change within the surrounding of Sentinel Peak. Notice the differences in the consistency of vegetation in 1904, compared to just 80 years later in 1984. The impacts upon the environment have made for a completely new perspective of scenery. Though, there are plenty of approaches to reduce and preserve the attraction of the esteemed A Mountain. In order to prevent further destruction of the habitats found in the area there will need to be an establishment of official trails; meanwhile, the unofficial trails, or trails deemed unfit for travel, will be restricted from access. The regulation of trails will salvage the restorable habitats and thus diminish space for potential invasive species to settle upon. Invasive plants that are frequently sighted during travel up the trails located throughout Sentinel Peak include Buffelgrass and Fountain Grass. The widespread of these plants are in the process of displacing the majority of native flora, as well as increasing the risk of disastrous fires. This is a popular concern as Sentinel Peak is often used as a platform to set off fireworks during holidays. In fact, on July 4th of 2017, most of "A Mountain" caught fire due to the overgrowth of the extremely flammable buffelgrass. Aside from fire hazards, these intruders expedite any potential repercussions, it would create an even bigger issue with a loss of vegetation. Progression of a vegetation loss is just the start of this domino effect. Erosion and a concentration of water flows will result from lack of vegetation, which will in turn inaugurate many more landslides. These landslides not only create a danger for drivers and hikers that frequently visit the mountain, but also for the surrounding neighborhoods found at the mountain’s base. To control this detrimental flow of events, re-vegetation, passive water harvesting, and the closing of redundant trails will allow a stabilization of desert habitat. 



Improvements for Sustainability

With clear threats intimidating the future of this popular Tucson landmark, the Tucson City Council have partnered with the Tucson Parks and Recreation staff. Meetings to introduce and speculate the needed renditions towards Sentinel Peak began July 28, 2008. After four years, phase one (out of three) started construction during fall of 2012. Improvements of this park are slowly, but presently still being made. Tucson city officials have hired professional workers to undergo these enhancements and also developed volunteer opportunities for tasks like invasive plant removal, trail building, and water harvesting. A major safety hazard within this landmark is the circulation of pedestrians and bicyclists, so new trails are being coordinated in order to avoid conflict with vehicles and adhere to more disability access. In fact, in response to an incident where a driver under the influence struck a 73 year old cyclist, killing him, Sentinel Peak became closed to vehicles on Mondays. In addition to the day off, hours of accessibility have been reduced to 11 am to 8pm. To increase safety for the variety of park users, new trails designated just for bikers/hikers were installed. More goals of these teams are to remove vandalism and trash, introduce more unobtrusive guardrails, add further traffic measures like pedestrian crossings and speeding signs, and to build beneficial amenities. Amenities like public restrooms, site history and interpretation signs, and trashcans will not only allow for a better experience for visitors, but also help maintain the goal of a clean and safe park. There are also goals of restoring or even fully removing and building a new overlook at the peak of the mountain. The goal of these renovations is to make Sentinel Peak a safe and exciting place for locals and tourists to visit. 


Sentinel Peak Lookout 1904Sentinel Peak Lookout 1984





 David Leighton, "Street Smarts: Tale of road up "A" Mountain includes murder, adultery and dirty deals," Arizona Daily Star, Oct. 3, 2016