Colorado (Colorado) is an inland state in the western region of the United States. The capital of the state is Denver (Denver) and the largest city. The state has a land area of 269,997 square kilometers and a population of 4.75 million. Among them, Denver has a population of more than 700,000. Due to the terrain, the state is civilized by the production of minerals, and the mining industry is very developed. Second, agriculture is also an important part of the state's economy. Manufacturing, transportation, service, and tourism are relatively developed. The main airport is Denver International Airport, which is one of the busiest airports in the United States and the world, ranking among the top 6 airports in the United States. Railway and road facilities are also very developed. Colorado's abbreviated zip code is CO and the area code is 303 - 719 - 720 - 970. The zip code reference of major cities is as follows, Denver zip code is: 80201-80295. The postal code for Boulder is 80301-80329. The zip code for Clolrado Springs is 80901-80997.