In Sigourney's downtown district, buildings of Victorian Italianate architecture, most of which came about in the 1870s, are adorned with quoin corners, bracketed metal cornices, and cast hood molds. The construction of the Keokuk County Courthouse in 1909 brought the Neo-Classical Renaissance to town, overhauling buildings and filling in bare lots. Today, both styles of architecture surround the Keokuk County courtyard.

Sigourney has been a Main Street community since 1990 and its historical downtown district was added to the National Register of Historic Places in 1999.