In the antebellum South, slave transport between the Upper and Deep South was profitable due to a persistent gap in slave prices between the two regions. The gap has been attributed to agricultural productivity differences. This paper examines another potential explanation: regional variation in the chance of successful escape. To do so, the Fugitive Slave Act of 1850 is exploited as a natural experiment. The Act strengthened slave-owners' property rights reducing the likelihood of successful escape. Providing identification, the Act had a bigger impact in border states, where escape to the Free states was arguably easier.Using data from probate records, estimates suggest a large fraction (between 20 and 30% depending on specification) of the observed price difference disappears after the 1850 Fugitive Slave Act. Estimates are robust to changes in sample restrictions, spatial composition effects, and placebo tests on the Act's implementation date. The findings are also supported by a reduction in the rewards offered and frequency of advertisements for runaways from newspaper advertisements at the time.