His supervisor was Benjamin Henry Latrobe, II, (1806-1878), later supervising engineer on the Baltimore and Ohio Railroad, (B.
The firm disbanded in 1856, when Niernsee was made architect of the capitol of South Carolina.
It was at this time, that they took into their office a number of young interns who later became prominent themselves, including R. Snowden Andrews, Eben Faxson, Bruce Price, and, briefly, E. Francis Baldwin.
Nielson was a founding member of the Baltimore Chapter of the American Institute of Architects at its charter in 1870.
[1] Neilson had married Rosa Williams in the 1830s, whose family owned farmland along Deer Creek in Harford County at a place called Priestford.