Final answer:
The Pacific Railroad Act provided a route for the construction of the transcontinental railroad.
Step-by-step explanation:
The Congressional action that provided a route for the construction of a transcontinental railroad was the Pacific Railroad Act. This act was passed by the United States Congress in 1862 and authorized the construction of the First Transcontinental Railroad, which connected the eastern and western coasts of the United States. The Pacific Railroad Act provided federal support, land grants, and loans to the Union Pacific and Central Pacific Railroad companies to build the railroad.
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