how many men worked on the transcontinental railroad
The short answer is that nobody really knows. The Central Pacific Railroad had a maximum of about 12,000 workers at one time, and the Union Pacific probably had a similar number, but people came and went, so the actual number who ever worked is significantly larger, but unknown.
The transcontinental railroad was also called the Pacific Railroad and the Overland Route. The total length of the First Transcontinental Railroad was 1,776 miles. The Central Pacific Railroad was controlled by four men called the Big Four.