Campau was an important figure in the early settlement of two important Michigan cities. He established the first trading post at what is today Saginaw, Michigan as early as 1815 and played a key role in negotiating the Treaty of Saginaw in 1819. The Treaty was made between Gen. Lewis Cass and Native American tribes of the Great Lakes region (principally the Ojibwe, but also the Ottawa and Potawatomi)Michigan. Native Americans ceded a large tract of land (more than six million acres, or 24,000 km²) in the central portion of the Lower Peninsula of Michigan. In 1826 Campau moved south and established a trading post in what is today Grand Rapids. He was not the first permanent white settler (that distinction falls to a Baptist minister named Isaac McCoy who arrived in 1825), but could be considered the most important.
Spelling of his surname varies. It is sometimes cited as "Campeau".