Which statement best explains why the transcontinental railroad took several years to build? Digging through the mountains was very difficult, and the long winters hampered workers’ ability to make progress. Several Civil War battles took place where the railroad was being built, so workers had to wait for the land to be clear and safe. A divided Congress continued fighting over funding for the railroad, leading to work stoppages every few months. Chinese immigrants engaged in frequent clashes with rail workers, so work stopped while safety measures were adopted.