In his youth, he obtained a public school education until he was sixteen and later worked in the family workshops to learn each step of the manufacturing process.
Along with his brother, Oliver Ames, Jr., he ran the Oliver Ames & Sons shovel business from about 1844.
In 1865, President Abraham Lincoln appealed to him to take control of the Union Pacific (UP) portion of the project, which had become mired down because of the war, and had built only 12 miles of track.
Through his influence he obtained contracts for his family firm in the construction of the Union Pacific and staked nearly all the family's holdings as capitalization for the project. The contracts were later transferred to the Credit Mobilier Company of America after Ames ousted its founder Thomas Durant. His brother Oliver was appointed president of the UP in 1866.
He was the principal financier of the Union Pacific Railroad, the eastern half of the first transcontinental railroad. Unfortunately, in his zeal to complete this railroad project, Ames made several errors in judgment. His questionable business practices eventually led to his censure by Congress.
A successful businessman, Oakes Ames became involved in politics as a member of the Republican Party when he was in his fifties.He served as a close business advisor to the governor of Massachusetts. At age of fifty-eight, Ames ran successfully for the Massachusetts second district seat in the United States House of Representatives. He was reelected four times and served in Congress until his death. As a Congressman Ames served on committees related to manufacturing and railroads.