The Col. Gustavius A. Palmer House was built c. 1858 by local stonemason and architect Andrew Jackson Simon. Like Palmer, Simon had come to McHenry County from New York. The house is an eclectic blend of popular styles, dominated by Neoclassicism. The house is built with brick with a two-story front section and a one-and-a-half-story rear.

Typical of the Federal Style, the house features broken pediment and a low-pitch gable. The gable features a dentilated cornice. Also typical of the style, the house features an off-center main entrance and large windows. Greek Revival influences are found in the heavy sills and limestone lintels surrounding doors, windows, and the water table. The foundation is a typical New England cobblestone masonry. The west elevation has an open air porch. The house has thirty windows—five on the south, ten on the west, one on the north, four on the east, and ten basement windows. The interior features plaster walls and southern yellow pine floors. There are no fireplaces.

The Count's House is a historic Greek Revival home in McHenry, Illinois. It is one of McHenry's oldest and most notable landmarks, as well as one of the finest preserved examples of Greek Revival architecture in McHenry County. It is the only building in the city of McHenry listed on the National Register of Historic Places.

Although the exact date of construction and original owner of the Count's House are unknown, the building is believed to have been built prior to the Civil War. The plaque on the exterior denotes the house as having been completed circa 1860.

The Count's House is particularly distinct for its two faces, a very unusual feature for a Greek Revival. The north facade, facing Waukegan Road, consists of a portico with full two-story columns of the Doric order. The south facade, facing Main Street, consists of two-story loggia with an upper balcony and several intricate mouldings.

The Lucien Boneparte Covell House was built in 1905 for Lucien Boneparte Covell and Anna Moore Covell. The couple lived in the home until they died, in 1923 and 1926.

The Covell House is an example of Late Victorian Queen Anne style architecture detailed with some elements of Colonial Revival. As a typical example of the style the house has a main roof ridge that runs parallel with the side elevations of the building with seven gables crossing it in various manners. Patterned shingles in the bays and in the gables heighten the structure's surface texturing and a full-width veranda extends along both side walls.

The Covell House property includes two separate original outbuildings, a carriage house and a buildings that served three functions, privy, wood shed and chicken coop. Both buildings were constructed concurrently with the house in 1905 and both are considered contributing buildings for the purpose of the National Register of Historic Places listing.

The 1857 Italianate Old Courthouse was constructed to closely resemble the 1853 Cook County Courthouse (which was eventually destroyed during the Great Chicago Fire). The structure was designed by John M. Van Osdel, the first licensed architect in Chicago. The adjoining structure, the Sheriff's House and Jail was built in 1887. Until 1973 McHenry County government office were located in the Old Courthouse. When the government moved out, the building was threatened with demolition, as it stood on prime commercial property. On November 1, 1974, it was recognized by the National Park Service on the National Register of Historic Places.

The Old McHenry County Courthouse faces the Woodstock public square. The Italianate structure was built out of brick with limestone trim. With four identical, 20-by-44-square-foot wings around a 44-square-foot core, the building resembles a Greek cross. The building stands two stories tall with a brick basement. A cupola is found at the center of the cross. A bay was later added to the southern wing, and small additions were made from the judge's chamber and a vault. The southwest corner has a one-story addition. The jail was originally found in the basement, but was moved to a new building along the north wall in the 1870s.