We study how regional shocks spill over across US local markets through intrafirm spatial networks created by multimarket firms. We identify spillovers by linking granular data on product-county-level prices and quantities with producer-level information and exploiting variation in firms’ exposure to differential declines in local house prices. A firm’s local sales decrease following a direct negative local demand shock but do so more strongly to indirect negative demand shocks originating in its other markets. Our barcode-level data and multiregion model with endogenous product quality adjustment reveal a novel uniform product replacement mechanism behind the spillover.