USA HISTORY

Detailed explanation-1: -Answer and Explanation: For the US government and the railroad companies, the biggest obstacles in building the Transcontinental Railroad were mountains of solid granite and attacks by Native American war parties.

Detailed explanation-2: -Each company faced unprecedented construction problems-mountains, severe weather, and the hostility of Native Americans. On May 10, 1869, in a ceremony at Promontory, Utah, the last rails were laid and the last spike driven.

Detailed explanation-3: -Eight Irish tracklayers put down 3, 520 rails, while other workers laid 25, 800 ties and drove 28, 160 spikes in a single day. On May 10, 1869, at Promontory Summit, Utah, a golden spike was hammered into the final tie. The transcontinental railroad was built in six years almost entirely by hand.

Detailed explanation-4: -The Sierra Nevada, the 400-mile-long range of granite peaks that form the backbone of California, was the most formidable obstacle in the construction of the Transcontinental Railroad.

Detailed explanation-5: -The Central Pacific met its greatest challenge at the outset-the towering Sierra Nevada, which presented enormous engineering obstacles and strangling winter snows. Deep fills, rock cuts, high trestles, snaking grades, and 15 tunnels through 6, 213 feet of solid granite blooded the CP crews.