The Manhattan Building, also known as the Phoenix Building or the Phoenix-Manhattan Building, is a historic skyscraper in Muskogee, Oklahoma. The building has eight stories, containing 50,957 square feet (4,734.1 m2) of floor space, and was initially intended as the home of the Manhattan Construction Company, reportedly Oklahoma's first incorporated business. It was built in 1911 with a reinforced concrete frame and gray brick cladding. These walls were lined with windows to provide light and ventilation, the latter were essential to cope with torrid Oklahoma summers in an era when hardly any large buildings had air conditioning. It was built in Sullivanesque architectural style, with two-story columns flanking the entrance and a second floor cornice with dentils. The entry opened into a two-story lobby whose walls were covered with tile. A rooftop penthouse was added in 1957. The Manhattan Building was added to the National Register of Historic Places for architectural significance in 1983.