As of the census of 2000, there were 520 people, 186 households, and 146 families residing in the town. The population density was 503.8 people per square mile (194.9/km²). There were 192 housing units at an average density of 186.0 per square mile (72.0/km²). The racial makeup of the town was 92.12% White, 2.88% Native American, 1.15% Pacific Islander, 1.92% from other races, and 1.92% from two or more races. Hispanic or Latino of any race were 4.23% of the population.
There were 186 households out of which 42.5% had children under the age of 18 living with them, 65.1% were married
couples living together, 9.7% had a female householder with no husband present, and 21.0% were non-families. 18.3% of all households were made up of individuals and 10.8% had someone living alone who was 65 years of age or older. The average household size was 2.80 and the average family size was 3.18.
31.7% of the population was under the age of 18, 6.7% were 18 to 24, 31.9% were 25 to 44, 17.5% from 45 were 64, and 12.1% were 65 years of age or older. The median age was 32 years. For every 100 females, there were 94.8 males. For every 100 females age 18 and over, there were 91.9 males.
The median income for a household in the town was $31,875, and the median income for a family was $36,806. Males had a median income of $31,429 versus $20,089 for females. The per capita income for the town was $14,309. About 13.1% of families and 17.8% of the population were below the poverty line, including 23.0% of those under age 18 and 18.8% of those age 65 or over.
Washington is the home of Washington Public Schools, which comprises a single K-12 school at 101 E. Kerby, Washington, OK 73093. The mascot is the warrior and school colors are red and white. As of the 2006–07 school year, the graduation rate was 94.7%, there were 17.4 students per teacher, and 916 enrolled students.
Sports played by students include: softball, football, basketball, baseball, cheerleading, golf, and track. Extra-curricular activities include academic team, band, FCCLA, FFA, newspaper, NHS, science club, STUCO, and yearbook.