Question

In the 1840s, the main argument in Congress over the transcontinental railroad concerned
the geographic direction of the railroad.
the money needed to fund the railroad.
the lack of available workers to build the railroad.
where the railroad should run.

Answer 1

Where the railroad should run — i.e., the route/direction (North vs. South), because Congress fought over which sectional interests and states the transcontinental line would serve.