Walker Hanlon is an Visiting Assistant Professor at Princeton University and a Faculty Research Fellow at the NBER. He also holds an appointment as an Assistant Professor at UCLA. He received his Ph.D. from Columbia University in 2012. Professor Hanlon's current research focuses on two areas. One line of work looks at the impact of pollution in cities over the long-term, with a particular focus on industrial pollution linked to coal use in the cities of 19th century Britain. In this line of research, he investigates both the health effects of pollution as well as the impact of pollution on long-run city growth and population sorting. he is studying the forces driving innovation and economic growth over the long term using novel historical data sources. Much of his work in this area takes advantage of the unique economic shock to the British economy causes by the U.S. Civil War. Using this event, he explores how the sudden shortage in cotton caused by the U.S. Civil War on innovation in the British cotton textile industry, and whether the temporary recession in cotton textile cities had a long-term impact on the trajectory of city growth.