The persistent instability of the agricultural sector is the fundamental premise of most agricultural policy. Yet no research has ever quantified the aggregate dynamics of individual farms in the US. This article is the first to combine the US Census of Agriculture with the Agricultural Resource Management Survey to observe the dynamics of nearly 1.5 million farms. The data reveal substantial variation in farm size expansion and contraction. Most of this variation is unobservable in the sector totals reported by the US Department of Agriculture each year. The distribution of agricultural subsidies suggests that subsidies become more important as farms get smaller and may play a role in slowing farm size contraction.