The tiny community's nineteenth-century buildings are grouped around its crown jewel, this Roman Revival courthouse. The county court ordered it to be constructed “after the plan of the new courthouse in Charlotte County” by Thomas Jefferson. Howard and Cosby were chosen at least in part because of Cosby's work with Jefferson at the University of Virginia. At the time, Cosby was constructing the courthouses in Goochland and Sussex (SU1) counties, and Howard had already built the one-story Cumberland Courthouse (CB1) and later would build the Mecklenburg Courthouse (MC1) with Cosby. Lunenburg's courthouse is similar to the Charlotte County courthouse (CT1), but the order to build it, like Charlotte's, was not strictly observed. Its portico is Doric, not Tuscan, and the dark-green shutters that usually accompany Jeffersonian courthouses are absent.
The four-columned portico's pediment features a keystoned lunette, and a full Doric entablature encircles the building. Unusually elaborate for a Virginia courthouse, the cornice soffit features mutules alternating with diamond fretwork. Within the portico, the building now has a double flight of stairs that leads to the courtroom entrance on the second floor. The courthouse was built with the two-story-high courtroom and rear balcony favored by Jefferson. Like several other courthouses, including those in Dinwiddie (DW1) and Mecklenburg (MC1) counties, the courtroom was later divided (here in 1857) into two separate levels in order to add offices for the clerks of the county court. Until the building was extended in 1939, the end wall had a shallow, circular apse for the justices.