According to Census data, these are the 10 counties that grew the most (in total population terms not percentage terms) between the 2010 census and the 2020 census.
#10 Hillsborough County, FL (Tampa)
This Tampa area county grew by 264,446 people during the 2010s.
The industry employing the most people in the county is healthcare & social assistance, but the highest paying industry by far is mining, quarrying, and oil and gas extraction.
#9 Travis County, TX (Austin)
This Austin, Texas county grew by 270,111 people, and the biggest employer industry by number of jobs is professional, scientific, and technical services (e.g. consulting, law, accounting, financial advising, etc).
#8 Collin County, TX (Plano)
This Dallas suburb county grew by 284,967 people during the decade. Like Travis County, the biggest employer industry is professional, scientific, and technical services. The highest paying sector is utilities. That likely means your best bet to get rich in Collin County is to be a consultant for a utility company.
#7 Riverside County, CA
The county includes the cities of Riverside and Palm Springs, California, as well as a large piece of Joshua Tree National Park. Total population increased by 287,626 people.
The biggest employer industry is healthcare and social assistance, followed by retail. If you aren’t a doctor or nurse, you can probably find better financial opportunities elsewhere.
#6 Bexar County, TX
This urban San Antonio county increased its population by 303,982 people. Median household income lags the national median by a decent margin, and the biggest employer industry is healthcare & social assistance, followed by retail, followed by hospitality & food service work. In other words, there isn’t a lot of economic opportunity if you aren’t a doctor or nurse.
#5 Tarrant County, TX
Tarrant is a large county that includes Fort Worth and many Dallas commuters (about 16% of Tarrant’s population commutes to Dallas for work). Total population increased by 305,180 people over the last decade. The biggest employer industry is retail, followed by health care and social assistance, followed by manufacturing. More lucrative industries are more common in neighboring Dallas County though.
#4 King County, WA
As the county that holds Seattle and all of the surrounding suburbs, King County grew by 335,884 people. The biggest employer industry (by a large margin) is professional, scientific, and technical services, and the median pay in that industry is well over $100k.
#3 Clark County, NV
The vast majority of this county’s population lives in or adjacent to Las Vegas, and total population increased by 363,323. The biggest employer industries here are what you’d expect for Las Vegas: accomodation, food services, retail, entertainment, and recreation.
#2 Harris County, TX
Our last two counties on the list grew SUBSTANTIALLY faster than any of the other 8. This urban Houston county grew by 630,711 people — over twice the number of people that Tarrant County gained during the same time period.
The biggest employer industry is construction.
#1 Maricopa County, AZ
The fastest growing county award goes to Maricopa — the county which contains Phoenix and Scottsdale in Arizona. The county’s population grew by 753,898 residents (nearly three times the growth rate of Tampa’s Hillsborough County and more than twice as much as the Seattle or Las Vegas areas).
The biggest employer industries by far are healthcare & social assistance followed by retail.