San Antonio's economy is still riding high thanks, in part, to the oil boom. Valero Energy (VLO), one of the nation's largest oil companies, is based here, as are a handful of other oil and energy services firms like Tesoro Corp (TSO). and NuStar Energy (NS).

The local economy, though, is still well diversified, with healthcare, tourism, financial services and call centers major sources of jobs. And Joint Base San Antonio, one of the largest military installations in the country, hosts 80,000 residents and trains some 130,000 military personnel a year.

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In January, the metro area unemployment rate was 5.4%, more than a percentage point below the national average.

San Antonio is also a young city, which is also helping to boost the local population, said Lloyd Potter of the Institute for Demographic and Socioeconomic Research University of Texas at San Antonio. "We have fewer deaths because we're young and more births as well," he said.