He worked on both of the most important and prestigious construction projects in the new capital: he quarried rock for the foundation of the White House and was overseer of the slaves who built the U.S. Capitol in 1795.
He also owned one of the major wharves in the city, Smallwood's Wharf, on the Anacostia River (then known as the "Eastern Branch") in southeast Washington, D.C.
[1] In 1807, Smallwood was one of eight wealthy city residents (along with George Blagden, Commodore Thomas Tingey and Henry Ingle) who attenuated a large lot in Washington for use as a public burial ground.
Smallwood also worked on legislation to establish the District's prison and Asylum, to keep the river navigable, to mandate that chimney's be swept regularly to avoid fires and to prevent the abuse of horses.
He also adopted plans for the construction of a City Hall designed by original U.S. Capitol architect George Hadfield.
His final act, signed August 24, 1824, established a committee to arrange the reception of General Lafayette.