Oil-rich cities topped the list of areas in which the nation’s 350 largest law firms added the most lawyers during 2012. Denver, Houston and Dallas showed the biggest gains, with Pittsburgh’s Marcellus shale work fueling growth there.

Of the top 25 U.S. markets that The National Law Journal tracked for our survey of the nation’s largest law firms by headcount during 2012, 15 cities saw gains—mostly modest—while nine lost lawyers. One region, Orange County, Calif., remained unchanged.