Panama Canal Railway
The Panama Railway also operated a significant shipping line, connecting its service with New York and San Francisco. It ran a Central American line of steamships linking Nicaragua, Costa Rica, San Salvador, and Guatemala to Panama City. The shipping service was greatly expanded when canal construction began. Ships included the SS "Salvador", SS "Guatemala", SS "Cristobel", and , which became the first of the ships to cross the completed canal in 1914.
In 1904 the United States took over the license to build and operate the canal. The choice to use locks and an artificial lake (Gatun) meant that the old railway route from 1855 had to be changed because it followed the Chagres River valley, which would be flooded by the lake. Also, the railway would be extended and altered continuously for the building process. The stock of the Panama Railway Company, vital in canal construction, was entirely controlled by the United States Secretary of War.
Saint Lawrence Seaway
The Panama Canal was completed in 1914 and also serves oceangoing traffic. In the 1950s, seaway designers chose not to build the locks to match the size of ships permitted by the 1914 locks at the Panama Canal (, known as the Panamax limit). Instead, the seaway locks were built to match the smaller locks of Welland Canal, which opened in 1932. The seaway locks permit passage of a ship long by feet wide (the Seawaymax limit).