Hallettsville is the birthplace of the late philanthropist and businessman Adolph R. Hanslik of Lubbock, a Czech-American sometimes called the dean of Texas cotton exporters.

It is also the only place called Hallettsville in the world. Ripley's Believe It or Not once called it the city of thirteen.

Hallettsville is located at 29°26′43″N 96°56′27″W / 29.44528°N 96.94083°W / 29.44528; -96.94083 (29.445398, -96.940734).

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 1,019 households out of which 29.9% had children under the age of 18 living with them, 44.0% were married couples living together, 14.6% had a female householder with no husband present, and 38.4% were non-families. 35.6% of all households were made up of individuals and 21.3% had someone living alone who was 65 years of age or older. The average household size was 2.29 and the average family size was 3.00.

In the city the population was spread out with 25.2% under the age of 18, 8.5% from 18 to 24, 23.4% from 25 to 44, 22.4% from 45 to 64, and 20.5% who were 65 years of age or older. The median age was 40 years. For every 100 females there were 83.1 males. For every 100 females age 18 and over, there were 78.3 males.

The median income for a household in the city was $25,089, and the median income for a family was $38,080. Males had a median income of $31,250 versus $20,365 for females. The per capita income for the city was $14,811. About 16.4% of families and 17.4% of the population were below the poverty line, including 21.0% of those under age 18 and 14.5% of those age 65 or over.