She was built in shipyards on the Mystic River at Medford, Massachusetts by shipbuilder Thatcher Magoun.

Magoun died the year she was launched, and the ship was named after him.

[1] According to Hall Gleason, Thatcher Magoun made five passages from Boston to San Francisco.

Moreover, in 1869, Thatcher Magoun made seven passages from New York to San Francisco, averaging 96 days per voyage.

[1] On one of its voyages from New York to San Francisco, Thatcher Magoun carried locomotives CP 88, 89, and 95 for the Central Pacific Railroad company.