Grand Lodge and Library of the Ancient Free and Accepted Masons
U.S. National Register of Historic Places
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Location	415 S. Main Ave., Sioux Falls, South Dakota
Coordinates	43°32′34″N 96°43′42″W / 43.54278°N 96.72833°W / 43.54278; -96.72833
Area	less than one acre
Built	1924
Architect	Hugill & Blatherwick
Architectural style	Classical Revival
NRHP reference No.	76001750 [1]
Added to NRHP	May 28, 1976

The Grand Lodge and Library of the Ancient Free and Accepted Masons in Sioux Falls, South Dakota is a building from 1924. It was listed on the National Register of Historic Places in 1976.^[1] The architects were Hugill & Blatherwick of Sioux Falls.^[2]

The National Register nomination describes its importance as "the purest example of Neo-classic style in Sioux Falls. The combination of classic elements and internal structural innovations of the early twentieth century, such as steel doors and trim painted to resemble wood and a nine-ton glass floor, enhance the architectural importance of the structure. The use of steel and glass were unique at that time in the city."^[3]

The building has one of the largest Masonic libraries in the United States. The library has more than 22,000 volumes. The building also has a museum on its second floor.^[3]