Born in Wilmot, Nova Scotia, he ran away from home at the age of twelve and earned a living as a cabin boy among the fishermen of the Bay of Fundy. At sixteen he shipped "before the mast", rising to his first command nine years later.
Slocum spent most of his life at sea. When shipwrecked on his way to Montevideo in 1887, he sold the wreckage, paid off his crew and built the Liberdale, a 35-foot junk-rigged boat, in which he and his family sailed home to Washington, DC. In 1894 he published Voyage of the Liberdale describing this adventure.
On April 24, 1895, in a rebuilt 36′ 9″ (11.2 metre) yawl-rigged fishing boat named Spray, he set sail from Boston, Massachusetts. More than three years later, he returned to Newport, Rhode Island on June 27, 1898 having circumnavigated the world, a distance of 46,000 miles (74,000 km). In 1899 he wrote his classic, Sailing Alone Around the World, describing this voyage.