The Union Pacific's progress across the Great Plains was much faster than the Central Pacific's progress through the Sierras. Why do you think this is?

The Union Pacific's progress across the Great Plains was faster primarily due to the relatively flat terrain and more favorable weather conditions, which allowed for easier construction of the railroad. In contrast, the Central Pacific faced significant challenges in the Sierra Nevada mountains, including rugged landscapes, harsh weather, and the need for complex engineering solutions like tunnels and bridges. Additionally, the Union Pacific had access to a larger labor force and resources in the plains, further accelerating their construction efforts.