What is the trancontinental railroad

It was a train route across the United States, and was finished in 1869. It was a project of two companies; the Union Pacific built from the East, and the Central Pacific built from the West. The Two lines met in Utah. It was a contiguous network of railroad trackage that crosses the continental land mass with terminals at different oceans or continental borders. And it was a major event of the westward expansion.

The one that stretched from coast to coast