Based on the most recent census in the year 2000, the state of Wyoming has the lowest number of inhabitants in the USA with 493, 782 citizens, and the lowest population density in the country with 5.1 people per square mile. In comparison, California has the highest with 33, 871, 648 residents and 217.2 people per square mile. The most populated areas in Wyoming are cities, most notably Cheyenne with an estimated 55,000 residents, Casper with roughly 49,000 and Laramie with 27,000. Wyoming's low population might be attributed to the state's generally mountainous and inhospitable geography, with the majority of the state forming a plateau amongst a series of mountain ranges, therefore reducing the amount of inhabitable land. The low population spread can also be linked to the space given to large national parks, including Yellowstone, Grand Teton and the Fossil Butte National monument. One of the consequences of this is that the average number of tourists coming into Wyoming per year greatly exceeds its core population.