Summary from Goodspeed

John H. Martin was a merchant and postmaster of Powhatan. He was born June 17, 1854 in California, the son of Josiah Martin, a gold miner. John moved to Powhatan in 1868. From 1870-1875 he was a clerk in a drug store in Lawrence County and afterwards engaged in the same business himself. In September 1880, he opned up a general stock of merchandise in partnership with his father under the firm of Martin & Son, but still continued in the drug business on his own account. The firm of Martin & Son do a business of about 30,000 dollars annualy. Mr. Martin was appointed assistant postmaster and in 1875 was given the office. He married Miss Lula McLeod in 1878, but she passed in 1880. He had one child, Charles H. Martin. 

Note this company and Martin family are entirely separate from Martin Bros wagon manufacturing. 

By 1890, the firm had moved to Black Rock, as evidenced by their stationary (B23, F130)

In 1892, Under the name Martin and Son, they sued P.V. Declaud for debt of 622.09. The firm was said to made up of Josiah and J.H. Martin (Box23 f129)