What two railroad companies met in the western part of the USA to form a coast to coast railway system?

This question may refer to the formation of "Transcontinental" railway that made train travel from the eastern part of the USA to the USA's west coast faster and less costly.

The first railway link was when two railroad companies joined their rails together in the Utah Territory in May of 1869. The two railway companies involved were the Union Pacific and the Central Pacific. By connecting the east coast to the west coast, travel time between the two coasts were reduced to a large extent. It also saved the US Government money insofar as postal delivery was concerned. It also provided a faster way for the military to transport troops and supplies.

Private citizens wishing to settle down in the western parts of the USA could do so faster and safer than wagon trains.