Which event happened before the Pacific Railroad Act was signed in 1862?

Asa Whitney proposed building a transcontinental railroad in the 1840s, before the Pacific Railroad Act was signed in 1862. The other events happened later: the Civil War ended in 1865, workers completed the Golden Spike ceremony in 1869, and the Sierra Nevada tunnels were blasted during construction after the act authorized the project.

AI-written and checked against the verified answer.