Montana is located in the northwestern part of the United States. The state has a land area of 381,156k square kilometers, ranking fourth in the United States, but its population is less than 1 million. The capital of the state is Helena and the largest city is Billings. The economy of Montana is mainly based on agriculture and animal husbandry. The transportation in the state is convenient, and the roads and railways are relatively developed. The abbreviated ZIP code for Montana is MT and the area code is 406. Postal code references for major cities are as follows: Heldna is 59601-59626. The postal code for Billings is 59101-59117. The zip code for Missoula is 59801-59812.