William Henry Aspinwall was a prominent American businessman who was a partner in the merchant firm of Howland & Aspinwall and was a co-founder of both the Pacific Mail Steamship Company and Panama Canal Railway companies which revolutionized the migration of goods and people to the Western coast of the United States.

The Pacific Mail Steamship Company was founded April 18, 1848, as a joint stock company under the laws of the State of New York by a group of New York City merchants. Incorporators included William H. Aspinwall, Edwin Bartlett, Henry Chauncey, Mr. Alsop, G.G. Howland and S.S. Howland.