It has never been definitively established where Northwestern Bell's earliest roots lie. The earliest record of telephones in the Northwestern Bell service area was a two-telephone intercom circuit used by a Little Falls, Minnesota druggist and his clerk in 1876. A Bell-licensed exchange is believed to have opened in Deadwood, South Dakota between March and August 1878, just two years after Alexander Graham Bell invented the telephone, and several months before President Rutherford B. Hayes could use his phone in a little wooden booth outside of his office in the White House.