For the last couple of years, headlines about the housing market have dominated the news cycles. From housing shortages to sky-high home prices, we’ve all heard about how the pandemic has affected nearly every housing market across the nation. Many of us have experienced the phenomenon firsthand. But while the pandemic has certainly had an impact on the housing market, there are plenty of other factors that have spurred housing growth in counties across the nation—and these factors aren’t as widely discussed.

Take, for example, the massive impact the oil boom has had on housing in the Midwest. Between 2007 and 2012, employment in North Dakota’s oil and gas industry increased by 354%, resulting in a 19% population growth in western North Dakota alone. As oil companies—and oilfield employees—continue to move in, sleepy towns and counties have been upended by the sudden influx of residents. While more jobs may boost the economy, the rapid growth can also leave cities struggling to keep up with demands for health services, roads, transportation, and housing.

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So which counties have seen the biggest housing growth over the last decade—and why? Better Mortgage, an online lender and homeownership platform with a free mortgage calculator, used data from the U.S. Census Bureau’s decennial census to calculate which counties have seen the greatest increase in housing units over the last 10 years. The counties are ranked according to the percent change in housing units between 2010-2020, and the top 20 counties with the biggest growth in housing were selected for the national story. Census data on housing was released on August 12, 2021, for all counties in America.

Here’s what you should know about your state.

Tennessee by the numbers

#20. Williamson County

– Change in housing units (2010–2020): 22,635 (+33.0% since 2010)
– Housing units in 2020: 91,133

Williamson County, Tennessee, which flanks the city of Nashville to the southwest, has seen explosive home growth over the last 10 years—and it’s due in major part to a high concentration of wealth in the area. As of 2019, Williamson County was the only county in Tennessee to have a median household income of over $75,000—and the only county in the state to have a poverty rate below 5%. In other words, there has been plenty of money in this county to support the purchases of homes over the last decade, and new residents have continued to pour into the area, keeping demand for housing high—but also pushing home prices higher and higher in tandem.

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In other areas of the nation, rapid rates of housing growth have other catalysts, including urban sprawl and economic growth. And, in rare cases, growth can even be caused by an unprecedented influx of retirees relocating to the area. The only consistent factor across these counties is that the subsequent housing growth has had a big impact on the housing market.

Keep reading to see which counties have been at the top of the housing market boom over the last decade.

Counties that have seen the biggest growth in housing over the last decade

#1. McKenzie County, North Dakota: 4,571 housing units added 2010-2020 (+147.9% since 2010)
#2. Williams County, North Dakota: 9,763 housing units added 2010-2020 (+93.3% since 2010)
#3. Hays County, Texas: 34,117 housing units added 2010-2020 (+57.4% since 2010)
#4. Dallas County, Iowa: 13,865 housing units added 2010-2020 (+50.9% since 2010)
#5. Comal County, Texas: 22,831 housing units added 2010-2020 (+48.5% since 2010)

This story originally appeared on Better Mortgage and was produced and distributed in partnership with Stacker Studio.