The history of the settlement is documented at the website of the Old Lewiston Schoolhouse.
As of the census of 2000, there were 1,305 people, 542 households, and 388 families residing in the CDP. The population density was 37.7 people per square mile (14.6/km²). There were 654 housing units at an average density of 18.9/sq mi (7.3/km²). The racial makeup of the CDP was 89.89% White, 0.23% African American, 2.61% Native American, 0.69% Asian, 0.15% Pacific Islander, 1.76% from other races, and 4.67% from two or more races. Hispanic or Latino of any race were 5.67% of the population.
There were 542 households out of which 28.2% had children under the age of 18 living with them, 56.3% were married couples living together, 9.4% had a female householder with no husband present, and 28.4% were non-families. 24.2% of all households were made up of individuals and 11.6% had someone living alone who was 65 years of age or older. The average household size was 2.41 and the average family size was 2.82.
In the CDP the population was spread out with 24.5% under the age of 18, 4.0% from 18 to 24, 21.2% from 25 to 44, 32.4% from 45 to 64, and 17.9% who were 65 years of age or older. The median age was 45 years. For every 100 females there were 102.0 males. For every 100 females age 18 and over, there were 103.5 males.
The median income for a household in the CDP was $30,500, and the median income for a family was $33,889. Males had a median income of $31,667 versus $20,000 for females. The per capita income for the CDP was $16,214. About 16.5% of families and 20.2% of the population were below the poverty line, including 31.5% of those under age 18 and 5.0% of those age 65 or over.
In the state legislature Lewiston is located in the 4th Senate District, represented by Republican Sam Aanestad, and in the 1st Assembly District, represented by Democrat Patty Berg. Federally, Lewiston is located in California's 2nd congressional district, which has a Cook PVI of R +13 and is represented by Republican Wally Herger.