In the early nineteenth century, five versions of stationary steam engines were in widespread use. In America, the high-pressure engine was dominant in the West, but on the eastern seaboard the low-pressure engine was viable. In Britain, the low-pressure engine was overwhelmingly dominant. Here we analyze the evidence on cost and performance of high- and low-pressure engines, and show that fuel-price and interest-rate differentials were sufficient to explain the distribution of steam engine types in America.