Cotulla, the county seat of La Salle County, is twenty-seven miles north of Encinal on U.S. Interstate Highway 35 in the northwestern part of the county. The town was named for Joseph Cotulla, a Polish immigrant. After learning that the International-Great Northern Railroad intended to extend its tracks into La Salle County in the early 1880s, Joseph Cotulla worked to build a town on the present site of Cotulla. In 1881 he provided 120 acres of land to induce the railroad to build into the county, and by 1882 a railroad depot had been built and lots in the new town had begun to be sold. By 1883 the town had been granted a post office, and several new buildings had been constructed, including a general store, a hotel, and a jail. In a special county election held that year Cotulla was designated the county seat, and the town began a period of rapid growth. By 1890 it had a population of 1,000, three general stores, two weekly newspapers, two churches, a saloon, a bank, a corn mill, and a cotton gin.
Cotulla developed a reputation as a rough place during its early years. According to one story, railroad conductors announced the town by calling out,"Cotulla! Everybody get your guns ready." Three sheriffs and nineteen residents are said to have lost their lives in gunfights in the town. Nevertheless, civilized institutions were also evolving; by 1885 Cotulla had a school enrolling 135 students, and by 1886 the town had a debating society that discussed such topics as "Should the education of a woman be co-equal of that of a man?" By 1892 Cotulla had a hotel, four general stores, three saloons, a meat market, two grocery stores, and daily stage service to supplement its railroad connection. School records for 1896 and 1906 show a separate school for fifteen black children.
Cotulla's economy has been largely based on sheep and cattle ranching. By 1914 the community had 1,800 residents, three hotels, two banks, two restaurants, an ice plant, an electric power plant, and a movie theater. In the mid-1920s new elementary and high schools were built. By 1931 Cotulla had a population estimated at 3,175 and seventy-five businesses. The population remained relatively stable and perhaps actually grew during the 1930s. A free public library was built in 1937, and by 1941 Cotulla had 3,633 residents and eighty businesses. In 1947 fifty-four businesses were reported. In 1949 the town built its first airport, and during the early 1950s the discovery of oil in the area helped to bolster the economy. In 1954 Cotulla had 4,425 residents, who supported ninety-two businesses. In 1961 the town had a population of 3,960 and seventy-two businesses. By 1971 it had an estimated 3,814 people and forty-seven businesses.
In 1974 the mayor of Cotulla was of Mexican descent, as were several members of the town council and two-thirds of the population. Since Cotulla had no industry, however, many residents lived in the town only part-time and seasonally migrated north to look for work. In 1982 Cotulla had a population of 3,912 and seventy-four businesses. In the early 1980s Ida and Ben Alexander donated the Alexander Memorial Library. The La Salle County Historical Commission sponsors the Brush Country Museum in the center of town. In 1990 the population of Cotulla was 3,694 and in 2000 it was 3,614.