Medary.com

According to the Sioux Falls Argus Leader:

The first Sonic Drive-In restaurant in South Dakota will be located on South Louise Avenue, next to Sportsman's Warehouse, in Sioux Falls, the company announced today.
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"We are excited about breaking ground for this Sonic because it brings us one step closer to serving the Sioux Falls community," said Bob Blumenthal, local franchisee. "Sioux Falls was one of Forbes magazine's 'Best Small Metros for Business and Career,' and it's a wonderful family-oriented community, making it an ideal location for a new Sonic Drive-In."