The Answer:

The first boat to cross the Panama Canal once it was opened was the S.S. Ancon, carrying a cargo of cement on August 15, 1914.

If we're counting test runs and boats that went through the canal while working on it before the official opening, then the Alexandre La Valley gets that honor, having made the trip on January 7, 1914.

You might be interested in our table of Famous Ship Canals and Waterways and the official Panama Canal website.

—The Editors