Sinton is located at .(28.034824, -97.508942)
According to the United States Census Bureau, the city has a total area of 2.2 square miles (5.7 km²), all of it land.
There were 1,845 households out of which 39.3% had children under the age of 18 living with them, 50.8% were married couples living together, 18.9% had a female householder with no husband present, and 23.6% were non-families. 21.4% of all households were made up of individuals and 11.5% had someone living alone who was 65 years of age or older. The average household size was 2.89 and the average family size was 3.35.
In the city the population was spread out with 30.0% under the age of 18, 10.0% from 18 to 24, 27.2% from 25 to 44, 19.3% from 45 to 64, and 13.5% who were 65 years of age or older. The median age was 32 years. For every 100 females there were 100.6 males. For every 100 females age 18 and over, there were 96.3 males.
The median income for a household in the city was $27,911, and the median income for a family was $32,266. Males had a median income of $25,331 versus $17,163 for females. The per capita income for the city was $12,881. About 22.4% of families and 28.0% of the population were below the poverty line, including 38.3% of those under age 18 and 21.8% of those age 65 or over.
Sinton was established in 1855 as a station on the San Antonio and Aransas Pass railroad and became the county seat of San Patricio.
The City of Sinton is served by the Sinton Independent School District.
From 1948 to 1958, Sinton was the home to the Plymouth Oilers, a semi-professional baseball team sponsored by Plymouth Oil Company, which had extensive drilling operations on the Welder ranch, north of the city. The team hired star college players for the summer and gave them jobs in the field, gas plant, and office. Experienced players were hired on a permanent basis. By 1950, the Oilers were playing a 46 game schedule, going 33-13 and placing fourth in the National Baseball Congress (NBC) national,semi-pro tournament. In 1951, the Oilers returned to the national,championship after winning the state title in Oiler Park before a record crowd of 2,304. At the national tournament in Wichita against the Camp Pickett (Virginia) Red Wings, Oiler pitcher Mike Blyzka turned in a no-hit, no-run game (5–0), the second in tournament history. The Oilers then defeated Atwater (California) 3–0 to win the national championship, the first Texas team to do so, They returned to nationals in '52, '54, '55, '56, and '57, placing second in '55. In '57, the NBC declared Sinton, Texas, the premier city in the nation, per capita, for promoting semi-pro baseball for nearly a decade. In the spring of 1958 the Plymouth Oil Company, citing economic conditions, ended its support of the Oilers, and the team disbanded.
Sinton High School has established itself as one of the premier athletic programs in Class 3A, securing State Championships in both Baseball and Basketball. The Pirates won back to back Class 3A baseball championships in 1988 and 1989, and won another in 2002. They have made 4 other trips to the State Baseball Tournament (1975, 1999, 2003, 2007). The Pirate basketball team won the Class 3A State Championship in 1996. In the 2001 Football season, Sinton finished their best season in school history, 14-1, with a close loss to Everman (25-14) in the 3A Division I State Championship game played at Kyle Field.