Fredericksburg, IA has a population of 1,159 and is the 14,247th largest city in the United States. The population density is 1,345 per sq mi which is 2362% higher than the Iowa average and 1385% higher than the national average. The median age in Fredericksburg is 35 which is approximately 7% lower than the Iowa average of 38. In Fredericksburg, 61% of the population over 15 years of age are married, 99% speak English and 1% speak Spanish. 84% of Fredericksburg residents were born in Iowa, 16% were born out of state, 0% were born outside of the United States and 1% were foreign born.