London’s Saint Martin-in-the-Fields is famed not only as a great work of architecture, but as the prototype for hundreds of churches throughout the world and especially in the United States. Designed by the Anglo-Palladian architect James Gibbs (1682–1754) and completed in 1726, Saint Martin was one of the first parish churches in England specifically planned to accommodate the Protestant worship style of eighteenth-century Anglicans.1 This is ironic since Gibbs himself was raised and remained a Roman Catholic, albeit discreet in the practice of his faith. Gibbs’s original proposal called for a circular church, inspired by Sir Christopher Wren’s first scheme...