| Official Name: | Mill Plain, Washington |
| Settlement Type: | Former CDP, Unincorporated community |
| Mapsize: | 250px |
| Subdivision Type: | Country |
| Subdivision Name: | United States |
| Subdivision Type1: | State |
| Subdivision Name1: | Washington |
| Subdivision Type2: | County |
| Subdivision Name2: | Clark |
| Unit Pref: | Imperial |
| Area Total Km2: | 15.5 |
| Area Land Km2: | 15.5 |
| Area Water Km2: | 0.0 |
| Area Total Sq Mi: | 6.0 |
| Area Land Sq Mi: | 6.0 |
| Area Water Sq Mi: | 0.0 |
| Population As Of: | 2000 |
| Population Total: | 7400 |
| Population Density Km2: | 477.6 |
| Population Density Sq Mi: | 1236.9 |
| Timezone: | Pacific (PST) |
| Utc Offset: | -8 |
| Timezone Dst: | PDT |
| Utc Offset Dst: | -7 |
| Elevation M: | 84 |
| Elevation Ft: | 276 |
| Coordinates: | 45.6447°N -122.4928°W[1] |
| Blank Name: | FIPS code |
| Blank Info: | 53-45915[2] |
| Blank1 Name: | GNIS feature ID |
| Blank1 Info: | 1852951[3] |
Mill Plain is an unincorporated area in Clark County, Washington, United States. At the 2000 census it was defined as a census-designated place (CDP) and had a population of 7,400. The area was not listed as a CDP for the 2010 census.
The Mill Plain area is located in southern Clark County. The community bordered by the city of Vancouver to the west and south and by the city of Camas to the southeast.
According to the United States Census Bureau, in 2000 the CDP had a total area of 6.0 square miles (15.5 km), all of it land.
As of the census of 2000, there were 7,400 people, 2,379 households, and 1,953 families residing in the CDP. The population density was 1236.9sp=usNaNsp=us. There were 2,500 housing units at an average density of 417.9sp=usNaNsp=us. The racial makeup of the CDP was 87.34% White, 1.62% African American, 0.57% Native American, 6.23% Asian, 0.11% Pacific Islander, 0.59% from other races, and 3.54% from two or more races. Hispanic or Latino of any race were 2.66% of the population.
There were 2,379 households, out of which 49.7% had children under the age of 18 living with them, 71.0% were married couples living together, 7.7% had a female householder with no husband present, and 17.9% were non-families. 12.6% of all households were made up of individuals, and 3.5% had someone living alone who was 65 years of age or older. The average household size was 3.11 and the average family size was 3.41.
In the CDP the age distribution of the population shows 34.5% under the age of 18, 7.2% from 18 to 24, 35.3% from 25 to 44, 17.3% from 45 to 64, and 5.7% who were 65 years of age or older. The median age was 30 years. For every 100 females, there were 99.2 males. For every 100 females age 18 and over, there were 95.4 males.
The median income for a household in the CDP was $58,432, and the median income for a family was $59,386. Males had a median income of $45,385 versus $26,803 for females. The per capita income for the CDP was $21,181. About 7.6% of families and 10.3% of the population were below the poverty line, including 15.8% of those under age 18 and 8.1% of those age 65 or over.