How do social networks impact technology adoption? We present a model of the effects of social network size on information and technology take-up and test its implications using a unique natural experiment in the mid-20th century US Midwest. We find that social network expansions, in the form of mergers between congregations of the American Lutheran Church, led to increased rates of agricultural technology adoption among farmers. In counties that experienced a merger, the number of farms using nitrogen fertilizer increased by over 7% and the total fertilized acreage increased by over 13% relative to counties without a merger. We provide evidence that these effects are driven by increased information sharing between farmers as a result of these congregational mergers.