We provide evidence that bank loan supply reactions to monetary policy changes are market-specific, emphasizing the importance of banks’ local specialization. We analyze the U.S. mortgage market and find that, when monetary policy eases banks increase new mortgage lending growth more in markets in which they are geographically specialized relative to other markets and banks. This holds after controlling for local lending opportunities and (unobservable) bank differences. Further empirical findings, supported by a simple model, suggest that banks face market-specific differences in lending advantages, related to market-specific information, leading them to exhibit different reactions to monetary policy adjustments. We document the aggregate effects of this geographical specialization channel both at the county level on mortgage supply and house price growth, as well as at the bank level on average specialization growth. Our study underscores the relevance of banks’ local specialization in shaping the transmission of monetary policy.