What groups provided labor to build this
transportation system?

The Chinese laborers worked out well and thousands more were recruited until the railroad's completion in 1869. Chinese labor provided the massive labor needed to build the majority of the Central Pacific's difficult railroad tracks through the Sierra Nevada mountains and across Nevada.

Explanation:

answer; the period of time known as the middle ages;

your answer is 1930's

explanation

this is just around the time the great depression was starting and putting the us ecnomy into ecnomic failure causing the goverment to take a much larger rule to try and pieace it back together