The northwestern state of Montana is often characterized by its natural beauty and vast expanses of land. The open terrain has given rise to the nickname “Big Sky Country.” Montana is the third-largest continental U.S. state, although it has a relatively low population density. Three national parks are located at least partially within Montana, including the famed Yellowstone National Park. Montana’s early economy was based around the mining of rich deposits of minerals and metals. The constant expansion of the railroad network in the late 19th and early 20th centuries brought an influx of agricultural workers who helped diversify Montana’s economy. Today Montana is still largely dependent on natural resources with agriculture, tourism, and timber production playing integral roles in the state economy. Montana also features expanding service sector industries such as tourism, real estate, construction, and healthcare.