Warren County is among the top 20 fastest-growing counties in the state, according to 2018 population estimates recently released by the U.S. Census Bureau.The census bureau estimates the county population grew by about 350 residents between 2017 and 2018, with a large majority of that number coming from new people moving into the area. That brings the local population up to an estimated 34,700.In terms of net population growth, Warren County ranks number 18 in the 2018 data, which is the latest data available.Out of last year’s growth in Warren County, just over 100 new people came from the natural birth rate. The rest of the growth, about 70 percent, came from new residents migrating to the county from outside areas, according to census data.Census data also shows the average age of Warren County residents also is going up. The median age of local people has crept upward slightly every year, from 39 in 2010 to 41 in the most recent data.Other neighboring counties experienced population growth in 2017-2018. Lincoln County added 1,500 new residents, bringing the population there up to almost 58,000.Franklin County brought in 382 people, growing its total to almost 104,000 residents.In Montgomery County, 106 new people moved in or were born, adding up to 11,500 total population.Topping the list of fastest-growing counties not just in the region, but across the entire state, is St. Charles County, which added about 3,900 residents between 2017 and 2018. Total population there is now estimated at just over 399,000.Among the other top five fastest-growing counties in Missouri, three are in the Kansas City metropolitan area — Clay, Jackson and Platte counties. Rounding out the top five is Greene County, where Springfield is located.Fast growth rateWarren County ranks higher for population growth when comparing the influx of new residents to the existing population. The most telling comparison is to look back at the last official U.S. Census collected in 2010.Warren county had about 32,500 residents in 2010, according to the census data. Close to 2,200 more lived in Warren County in 2018, a growth rate of 6.8 percent. That’s the ninth-highest growth rate in Missouri.Among neighboring counties, St. Charles has a growth rate of 10.7 percent over eight years, and Lincoln County’s growth rate is 9.74 percent. Franklin County has grown by 2.2 percent since 2010.Last year was the first year Montgomery County experienced population growth since the 2010 census. Even with that growth, about 700 fewer people live there now than at the beginning of the decade, a net loss of 5.7 percent.Local city populationsU.S. Census Bureau data for individual cities and villages does not yet include population estimates for 2018. Below are the estimated population counts of local municipalities based on 2017 data.• Innsbrook — 664• Marthasville — 1,338• Pendleton — 25• Truesdale — 860• Warrenton — 8,091• Wright City — 3,489In terms of population age, Innsbrook is estimated to have the highest median age at 62. However, there also are an estimated 114 children under 5 years old living in the village, which would account for about 17 percent of the population.The city with the youngest residents on average in Warren County is Truesdale, with a median age estimate of 29, according to the census bureau. That can be partly attributed to Truesdale having the highest percentage of children under age 18, which is estimated to be about 37 percent of the city’s population.Warrenton, Wright City and Marthasville are estimated to be made up of 29 percent to 31 percent children under age 18. The median age in those cities is between 33 and 36.Truesdale and Wright City are the most racially and ethnically diverse places in Warren County, in terms of characteristics tracked by census data. In surveys administered by the U.S. Census Bureau, about 15 percent of respondents from Truesdale identified as being non-white or coming from two or more races. In Wright City, almost 25 percent of respondents said they were nonwhite or mixed race.The population of Hispanic people of all races in Truesdale was estimated at about 11 percent in 2017. Wright City’s population of Hispanic people was also estimated at close to 11 percent.These numbers are relatively significant demographic shifts that have come along with population growth since 2010. Both cities have been front runners in local population growth.Truesdale added an estimated 204 people since 2010, a 31 percent jump from the beginning of the decade. Wright City grew by an estimated 558 residents, a 19 percent growth rate in the same time period.The population in Truesdale that reported being nonwhite or mixed race on the 2010 census was 11 percent, and the Hispanic population was around 5 percent. In Wright City, the population on the 2010 census was about 18 percent nonwhite or mixed race, and 2 percent Hispanic.Warren County MO