We model competition in local deposit markets between for-profit and not-for-profit financial institutions. For-profit retail banks may offer a superior bundle of financial services, but not-for-profit (occupational) credit unions enjoy sponsor subsidies that allow them to capture a share of the local market. The model predicts that greater participation in credit unions in a given county will be associated with higher levels of retail-bank concentration. We find empirical evidence of this association. The ability of credit unions to affect local banking market structure supports the presumption of current banking antitrust analysis that retail banking markets remain local. We identify local economic factors that modulate the nature of competition between banks and credit unions, including income per capita and population density.