In 1942, London's Westminster Abbey held Thanksgiving services for U.S. troops stationed in England. More than 3,500 soldiers filled the church's pews to sing America, the Beautiful and The Star-Spangled Banner the first time in the church's 900-year history that a foreign army was invited to take over the grounds. It was an ironic gesture given the holiday's origins as a festival for pilgrims fleeing religious tyranny in Britain.