The county is bounded on the north by Pine Island Bayou, on the northeast by the Neches River, and on the east by Sabine Lake and the mouth of the Sabine River, a natural outlet called Sabine Pass.
There were 92,880 households out of which 33.00% had children under the age of 18 living with them, 48.40% were married couples living together, 16.20% had a female householder with no husband present, and 31.30% were non-families.
27.30% of all households were made up of individuals and 11.00% had someone living alone who was 65 years of age or older.
of 2000, there were 252,051 people, 92,880 households, and 63,808 families residing in the county.
The population density was 279 people per square mile (108/km²).
Jefferson County is part of Texas' 14th congressional district, represented in the US House of Representatives by Randy Weber (Republican).
The Texas US Senators are John Cornyn (Republican) and Ted Cruz (Republican).18.9% of the population were ethnic Hispanic or Latino of any race.The County Commissioners Court, considered the administrative arm of the state government, is made up of a county judge and four commissioners.Males had a median income of ,719 versus ,924 for females. About 14.60% of families and 17.40% of the population were below the poverty line, including 24.60% of those under age 18 and 11.80% of those age 65 or over.The 2015 US Census estimates for demographic analysis of the population are the following: The racial makeup of the county was 59.3% White, 34.3% Black or African American, 1.0% Native American, 3.9% Asian, 0.1% Pacific Islander, 4.26% from other races, and 1.50% from two or more races.In many parts of Texas, Republican voters have predominated in presidential elections, especially since the turn of the 21st century.  In 2008, Barack Obama won 51.25% of the vote and 44,888 votes.