He rose to the position of mate at eighteen and shortly after made San Francisco his home port.  He tried his hand at salmon and other fisheries.  By 1860 he became a captain, first of the coasting schooner, then of the 332 ton barque "Washington."

He married his first wife, Virginia A Walker, in Sydney, Australia, in 1871, and she sailed with him until her death in Buenos Aires in 1884.  Of their seven children, all born on board of their father's ships, four survived infancy.

In 1886, Slocum remarried.  His second wife, Henrietta Elliott, was his first cousin from Mount Hanley.  On their first voyage together in his ship, the "Aquidnack", they experienced mutiny, smallpox, and shipwreck.  After losing his ship off South America, Slocum built a craft, the "Liberdade", which he described as being "half Japanese sampan and half Cape Ann dory", only thirty-five feet long, in which he and his family sailed 5500 nautical miles to Washington, D.C.  In the spring of 1889, they sailed to New York: but Henrietta went by rail to Boston and never went to sea again.

The age of steam had arrived, and Captain Slocum could not get another command.  He wrote a book "The Voyage of the Liberdade", which was published in 1890.

In 1892, he began to rebuild an ancient oyster sloop, the "Spray", for fishing.  But in 1895 he started on a round-the-world voyage, something which had never before been done solo.  It has been done since, but with modern navigation aids.

He sailed first from East Boston to Gloucester, then to Nova Scotia, stopping to visit friends and relatives in Westport and Yarmouth.   He then crossed the Atlantic to the Azores, then to Gibraltar.  He had planned to go through the Suez Canal, but was turned back because of pirate activity there.   He recrossed the Atlantic to Pernambuco, Rio Montevideo, Buenos Aires (to visit Virginia's grave); then on to Cape Horn.  It took him two months (Feb. 14 to Apr. 13, 1896) to navigate Magellan Straits, avoiding looting or murder by natives by scattering carpet tacks on the deck at night.

He visited Juan Fernandez Island (where Alexander Selkirk was marooned), Samoa, then on to Tasmania, Australia, Keeling Cocos Islands, Mauritius, South Africa, St. Helena, Ascension Island, and back to the coast of Brazil.   At this point he had circumnavigated the globe: stopping in larger ports for varying periods of time; financing the voyage by giving lectures and charging visitors sixpence to board the "Spray".  From Brazil he steered for the British West Indies, then home to the United States, reaching New Bedford on July 8, 1898, after a voyage of over 46,000 miles.

In 1899, Joshua Slocum wrote another book "Sailing Alone Around the World".  In December of that year, he visited Nova Scotia and remained until February of 1900, lecturing and reading the proofs of his book, which was published later in that year.  (A copy bound in navy blue cloth with an anchor and sea horse stamped on the cover is an early edition worth many times the original price).

In 1902, he bought a farm on Martha's Vineyard and settled down for a few years, but farming and fishing were not for him.  In 1907 he made a trip to the West Indies.  In 1909, he set out for South America, planning to explore the Amazon and Orinoco Rivers, and was never seen again.  A gale arose shortly after he left Vineyard Haven, and he may have perished not far from his point of departure.  Edward R Snow, in a book "Mysteries of the New England Coast" said that new evidence indicated he may have reached the West Indies and been run down by an inter-island mail steamer off the coast of Turtle Island in the Lesser Antilles.