Killeen is a city in Bell County, Texas, United States. According to the 2010 census, its population was 127,921, making it the 21st-most populous city in Texas and the largest of the three principal cities of Bell County. It is the principal city of the Killeen–Temple–Fort Hood Metropolitan Statistical Area. Killeen is 55 miles (89 km) north of Austin, 125 miles (201 km) southwest of Dallas, and 125 miles (201 km) northeast of San Antonio.
Killeen is directly adjacent to the main cantonment of Fort Hood. Its economy depends on the activities of the post, and the soldiers and their families stationed there. It is known as a military "boom town" because of its rapid growth and high influx of soldiers.
In 1881, the Gulf, Colorado and Santa Fe Railway extended its tracks through central Texas, buying 360 acres (1.5 km2) a few miles southwest of a small farming community known as Palo Alto, which had existed since about 1872. The railroad platted a 70-block town on its land and named it after Frank P. Killeen, the assistant general manager of the railroad. By the next year, the town included a railroad depot, a saloon, several stores, and a school.