If someone wanted to construct a new transcontinental railroad, what senate committee would most likely handle the request for congressional aide

Senate Commerce Committee

Explanation:

The Senate Committee on Commerce, Science, and Transportation is a standing committee and one of the largest in the United States Senate. This Committee has 25 Senators and is led by Committee Chairman Roger Wicker, and Ranking Member Maria Cantwell.

It has six subcommittees, in charge of issues such as communications, highways, transportation security, merchant marine, aviation, economic development, technology, and competitiveness. And they would be in charge of managing any request for congressional aid for a new transcontinental railroad.