The Old Post Office Pavilion, also known as Old Post Office and Clock Tower and officially renamed the Nancy Hanks Center in 1983, is a historic building located at 1100 Pennsylvania Avenue NW in Washington, D.C. It was completed in 1899, and used as the city's main post office until 1914. It was used primarily as an office building afterward, and was nearly torn down during the construction of the Federal Triangle complex in the 1920s. It was nearly demolished again in the 1970s to make way for completion of Federal Triangle. Major renovations occurred in 1976 and 1983. The 1983 renovation added a food court and retail space. An addition was added to the structure in 1991.