Mauranm entered the Massachusetts Institute of Technology (MIT) as a student of electrical engineering but switched to architecture in his sophomore year. After graduation in 1889, he completed his education abroad before returning to Boston and entering the office of Shepley, Rutan & Coolidge. Two years later, Mauran was sent to the firm´s Chicago office where he worked on the Chicago Public Library and Chicago Art Institute.

In 1893, he joined Shepley, Rutan & Coolidge´s St Louis office. Mauran married Isabel Chapman in 1899 and the couple moved into her family home (designed by Eames & Young) at 46 Vandeventer Place. The following year saw the formation of Mauran, Russell & Garden and the departure of Shepley, Rutan & Coolidge from St. Louis. The new firm took over the work in progress and the suite of offices in the Chemical Building. Nelson C. Chapman (wealthy scion of a lumber baron, a co-owner of the building and Mauran´s uncle-in-law) brought the first big commission: an addition to the 1896 Chemical Building. Mauran was president of the St. Louis Chapter of the American Institute of Architects in 1902 and 1903.

Mauran was appointed to the first St. Louis Public Buildings Commission in 1904.