Dating all the way back to George Washington, dogs have been constant companions to nearly all of America's presidents; of the past 46 chief executives, 31 have had at least one dog at 1600 Pennsylvania Ave. In this illustrated survey, the Presidential Pet Museum's Andrew Hager considers how Americans' relationships with dogs have evolved over the past 230 years, while considering such canines as Fala, FDR's well-traveled Scottie; Tut, Hoover's campaign photo-op; and Abe Lincoln's Fido, who was also assassinated in 1865.