Lake Koshkonong, WI has a population of 1,233 and is the 13,874th largest city in the United States. The population density is 87 per sq mi which is equal to the Wisconsin average and 4% lower than the national average. The median age in Lake Koshkonong is 48 which is approximately 23% higher than the Wisconsin average of 39. In Lake Koshkonong, 69% of the population over 15 years of age are married, 97% speak English and 1% speak Spanish. 66% of Lake Koshkonong residents were born in Wisconsin, 32% were born out of state, 0% were born outside of the United States and 2% were foreign born.