In 1905, W. J. Luna founded and named Plains. When Yoakum County was organized in 1907, Plains was designated the county seat. Following the discovery of oil in 1936 the population has grown steadily.[6]
According to the United States Census Bureau, the town has a total area of 1.0 square mile (2.6 km2), all land.
Sulphur Springs Draw runs through town. The springs feeding the stream formerly running through it have dried up due to the extraction of underground water.[6]
As of the 2020 United States census, there were 1,355 people, 428 households, and 346 families residing in the town.
2000 census
At the 2000 census, there were 1,450 people, 485 households, and 390 families living in the town. The population density was 1,466 inhabitants per square mile (566/km2).[3] There were 569 housing units at an average density of 575 per square mile (222/km2). The racial makeup of the town was 69.66% White, 0.76% Native American, 0.07% Asian, 0.07% Pacific Islander, 27.79% from other races, and 1.66% from two or more races. Hispanic or Latino of any race were 53.03% of the population.
Of the 485 households, 42.3% had children under the age of 18 living with them, 68.0% were married couples living together, 8.9% had a female householder with no husband present, and 19.4% were non-families. 17.1% of households were one person and 8.7% were one person aged 65 or older. The average household size was 2.98 and the average family size was 3.37.
The age distribution was 32.6% under the age of 18, 8.1% from 18 to 24, 27.4% from 25 to 44, 20.7% from 45 to 64, and 11.2% 65 or older. The median age was 34 years. For every 100 females, there were 97 males. For every 100 females age 18 and over, there were 91 males.
The median household income was $32,188 and the median family income was $36,250. Males had a median income of $27,188 versus $21,042 for females. The per capita income for the town was $14,624. About 17.2% of families and 20.2% of the population were below the poverty line, including 28.9% of those under age 18 and 23.5% of those age 65 or over.