His father was a lawyer and prominent local Republican who was a strong advocate of voting rights for African Americans.

He then traveled to Europe to observe and study the continent's famous buildings and returned to Washington in 1886 where he opened his own practice.

[3] Clark originally designed buildings in the Romanesque Revival style, influenced by his time working with Mullett.

[1] One of his house designs, built in 1900 for The Washington Post editor Beriah Wilkins, was a 35-room French Colonial mansion at 1711 Massachusetts Avenue NW (demolished) that was one of the largest residences in the city at the time of its construction.

Clark was also an author, contributing an essay titled "History of Architecture in Washington" for volume II of John Clagett Proctor's Washington: Past and Present, and writing Institutional Homes for Children, a book advocating for improved residential facilities for orphans.

"[2][6] Several of Clark's designs, including buildings he designed expansions or alterations, are now listed on the NRHP, including: 1644-1666 Park Road NW, 1833 Park Road NW, the Christian Heurich Mansion, Engine Company 21, the Denrike Building, the John Mercer Langston School, the National Saving And Trust Company, Riggs National Bank, Second Baptist Church, Second National Bank and the U.S. Civil Service Commission Building.