He established British North America's largest wholesale hardware house, Frothingham & Workman.

In 1890, its ten acres of grounds were purchased for $86,000 by Lords Strathcona and Mount Stephen, on which they built the Royal Victoria Hospital.

John Frothingham (1749-1826), a graduate of Harvard University who became a Judge of the Superior Court of Massachusetts and kept a summer house at Portland.

From an early age, John was employed in his uncle's, Samuel May's, hardware firm in Boston.

In 1836, Frothingham went into partnership with William Workman, and their firm became the largest hardware and iron wholesale house in British North America.

Frothingham promoted and invested in a wide variety of business interests that were being formed during the expansion of Montreal in the 1840s.

He resigned in 1849 after the bank sustained heavy losses and was succeeded by his close friend and business partner, William Workman.