The Keystone Bridge Company, founded in 1865 by Andrew Carnegie

Andrew Carnegie

Andrew Carnegie was a Scottish-American industrialist, businessman, and entrepreneur who led the enormous expansion of the American steel industry in the late 19th century...

, was an important American bridge building company. It was one of the 28 companies absorbed into the American Bridge Company

American Bridge Company

The American Bridge Company is a privately held civil engineering firm specializing in the construction and renovation of bridges and other large civil engineering projects, founded in 1900, and headquartered in Coraopolis, Pennsylvania, a suburb of Pittsburgh.-Products and industry positioning:The...

 in 1900. The company advertised its services for building steel, iron,wooden railway and road bridges. It held a patent for wrought iron bridges and also supplied wrought iron columns for buildings. Thomas Carnegie

Thomas M. Carnegie

Thomas Morrison Carnegie was a Scottish-born American industrialist. He was the brother of steel magnate Andrew Carnegie, and co-founder of the Edgar Thomson Steel Works .-Early life:...

 worked for Keystone Bridge as treasurer for roughly 20 years, from the founding of the company until his death in 1886.

Keystone is perhaps best remembered for the Eads Bridge

Eads Bridge

The Eads Bridge is a combined road and railway bridge over the Mississippi River at St. Louis, connecting St. Louis and East St. Louis, Illinois....

 in St. Louis

St. Louis, Missouri

St. Louis is an independent city on the eastern border of Missouri, United States. With a population of 319,294, it was the 58th-largest U.S. city at the 2010 U.S. Census. The Greater St...

, completed in 1874 , which survives to this day.