SALT LAKE CITY — Six counties in Utah are on the U.S. Census Bureau's list of 100 fastest-growing counties.

The Census Bureau recently released its estimates of housing units for counties that had 5,000 or more units, measuring expansion from 2010-12.

In 21st place nationally, Wasatch County ranked highest among Utah counties, followed by Grand, Washington, Cache, Box Elder, Utah and Uintah counties.

The Wasatch Front counties — Salt Lake, Utah, Davis and Weber — maintained the highest number of housing units. However, a geographic outlier, Washington County, ranked No. 5 in the total housing unit ranking for Utah.

According to the Census Bureau estimates, Piute, Sanpete, Carbon and Emery counties showed the slowest 2010-2012 expansion in housing units. Millard County actually shows a small loss.

While Washington County ranked fifth in the number of total housing units, it ranked fourth for new housing stock added between 2010 and 2012. On the other hand, while Weber County held fourth place for total units, it dropped to sixth for new units added.