Plainfield, WI has a population of 1,070 and is the 14,725th largest city in the United States. The population density is 687 per sq mi which is 686% higher than the Wisconsin average and 658% higher than the national average. The median age in Plainfield is 31 which is approximately 20% lower than the Wisconsin average of 39. In Plainfield, 58% of the population over 15 years of age are married, 69% speak English and 30% speak Spanish. 72% of Plainfield residents were born in Wisconsin, 16% were born out of state, 1% were born outside of the United States and 11% were foreign born.