French companies started digging the Panama Canal in 1881 but there were too many challenges and the work ground to a halt. U.S. Pres. Teddy Roosevelt saw opportunities for trade and for American prestige in being able to finish and control the canal, and he pushed for the U.S. to take over its construction in 1904.

The canal locks were the most technically difficult part of building the canal. These huge concrete structures were over 300 meters long, and each series of two or three locks can move a ship 25 meters up from sea level to the canal level and the same distance down at the other end.

Most of the work in building the canal, however, was simply digging the vast amount of dirt and rock out of the trench. In parts of the canal the sides kept sliding in (they still do from time to time) and the dirt that fell into the channel had to be dug out. The landslides were such a problem that some people thought the canal could never be built. Even after it opened two huge landslides in 1915 blocked the passage for months.

By 2008, 815,000 vessels had passed through the Panama Canal. It remains an important link for trade but is limited by the size of the locks—a problem as cargo ships grow ever larger. A third set of larger locks is being constructed and should open by 2015.

Neighboring countries have looked into projects that may one day be competition for the canal. Colombia may build a railway from coast to coast that will transport large ships. Nicaragua hired a Hong Kong–based group to work on a project to build its own canal, perhaps starting as early as December 2014.

Here, from the Scientific American Archive, is a slide show of the early history of the canal celebrating the 100th birthday of one of the world’s greatest engineering projects.

The Scientific American Archive is an extensive primary source on every great engineering work since 1845.