Aquilo was a steam yacht which was built in Boston in 1901 for William Phelps Eno, a wealthy man who was the inventor of the stop sign. In 1910, Eno sold Aquilo and the yacht was brought to the west coast of North America, where it was operated principally in Puget Sound and coastal British Columbia. Aquilo had a long succession of wealthy owners. In 1966, the yacht caught fire and sank while en route from Seattle to Los Angeles.

By the 1950s, the only steam yachts still operational on Puget Sound were Aquilo and El Primero.