The most architecturally important building surviving in the city is the courthouse. It served as the courthouse when Delaware was part of Chester County, and then again for half a century after Delaware was formed until the county seat was moved to Media. Its carefully cut squared stone walls interrupted by pent eaves on the gable ends give it something of the air of a fashionable house, but the oversized polygonal extension on the west side that housed the court (like that of the brick courthouse, 1730, in New Castle, Delaware) marks its special use. As in typical English county towns, the court stood at the head of the town market that stretched west toward Chester Creek. The oldest surviving county building in Pennsylvania, it is of extraordinary interest in demonstrating the high level of stonework and carpentry of the early colonies. It was restored by Clarence Brazer before the Great Depression.

Around the courthouse are a few remnants of the prosperous early-twentieth-century city that was supported by the vast industrial complexes of the riverfront. The brick National Guard Armory (1907) at Sproul and James streets with its castellated facade is an uncharacteristically militaristic work of Price and McLanahan.