McKesson Corp., the nation's largest pharmaceutical distributor, announced last week that it will relocate its headquarters from San Francisco to Las Colinas in April. The company, which delivers prescription drugs and medical supplies, has more than 75,000 employees globally and had revenue of $208 billion last year. It ranks sixth on the Fortune 500 list, behind only Walmart, Exxon Mobil, Berkshire Hathaway, Apple and UnitedHealth Group. With its move, McKesson will become the second-largest company by revenue to be based in North Texas, surpassing AT&T Inc. The largest, Exxon Mobil, is also headquartered in Las Colinas. Dallas-Fort Worth had 22 Fortune 500 company headquarters this year. That'll grow next year with the addition of McKesson and another California transplant, San Francisco-based Core-Mark Holding Co., which is relocating to Westlake.