What was a difficulty the builders of the transcontinental railroad had to overcome?

One major difficulty the builders of the transcontinental railroad faced was the challenging terrain, particularly in the Sierra Nevada mountain range. They encountered steep grades, harsh weather conditions, and the need to construct tunnels and bridges, which significantly increased the complexity and cost of the project. Additionally, logistical issues such as sourcing materials and labor, especially in remote areas, posed ongoing challenges throughout the construction process.