The most ambitious building in Rensselaer is the limestone Jasper County Courthouse, finished in 1898 to a Romanesque Revival design by the Chicago firm of Charles R. Williams. It sits on the original 1865 courthouse square, a heavyset block with arched windows, a tall central clock tower and a copper-clad cupola. Inside, the original cast-iron staircases and pressed-tin ceilings survive. The square around the courthouse has remained intact enough to be listed as the Rensselaer Courthouse Square Historic District.