Dallas County ranks among the top 20 counties in the nation when it comes to overall incoming money invested into the local economy by individuals, businesses and government, according to an analysis by SmartAsset. Ranked No. 19 nationally in the study, Dallas County was the No. 1 county among Iowa’s 99 counties. Johnson, Polk, Dickinson and Warren rounded out the top five in Iowa. Polk County ranked 65th nationally for highest overall investments. The study built an index for each county based on four factors: the number of businesses established in each location over a three-year period; real GDP growth; the number of new building permits per 1,000 homes; and federal funding received by each county, measured by contracts awarded per capita. Nationally, Los Angeles County ranked No. 1 in overall investment.