One of the major positives of the transcontinental railroad came in the form of economic development. Connecting California to the developed East via land routes would help the United States economy eventually grow into the largest in the world. In 1869, the transcontinental railroad was completed at Promontory Point, and rail was the fastest method of travel. Having a railroad that connected east to west increased commerce and provided a huge boost to the country's economy, while railroads became one of the country's largest industries.
The transcontinental railroad sped up the development and settlement of the Western territories, creating the first easy way for workers to move across the country. Cities sprang up along the railroads, and, once established, led to more local settlements around the area. Without a railroad connecting one side of the country to the other, few options remained for common workers who didn't have the wealth to take other forms of transportation out to California, or even any other part of the territory along the way.
While history shows many shameful instances of how Chinese and Irish immigrant workers were treated, the construction of the railroad did directly contribute to thousands of Irish and Chinese receiving paying jobs and contributing to the nation's "melting pot" of culture. In addition to these groups, many freed slaves also found work helping to build the transcontinental railroad and would eventually settle out West.
Many industries still use the railways that made up the transcontinental railroad, and the railroad lines that sprung up off of it to other parts of the country. From moving livestock to chemicals and coal, freight trains continue to make up a major part of shipping across the country. Amtrak also uses these routes as a passenger train option for individuals who want to travel across the country without flying or driving.