This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). This doctoral dissertation research in economics (DDRIE) project will study how the economic conditions, land rights, and water rights of American Indian tribes were influenced by western expansion. The evolution of American Indian development as a result of western expansion allows for the study of long-standing questions about institutional development in many ways---land and natural resource management during and since settlement, property rights enforcement, contract recognition, and corruption in public finance. This research is based on the construction of a new dataset based on highly disaggregated annual data that looks at individual land transfers over time and includes tribal characteristics, socio-economic data, land-use information, legal institutions, and details of financial arrangements between tribes and the U.S. government. This project will make available a new dataset of parcel-level data, collecting information held in the national archives and other sources that have been difficult to aggregate previously due to technological limitations. This project will broadly expand the accessibility of pivotal information regarding U.S. western settlements and the United States? relationship with American Indian tribes. The first section focuses on how land characteristics, socio-economic conditions, and public finance influenced American Indian reservation boundaries. The research team has have geocoded the transfers of individual parcels of land from Bureau of Land Management records and matched to reservation boundaries, data on land-price information, to historic reports from the Office of Indian Affairs, and to digitized U.S. ? American Indian treaties. The land parcel data allows the researchers to analyze the checkerboarding of reservations, changes in patterns as new rules are introduced, the heterogeneity of experiences across tribes and reservations, and the impact of treaty and financial arrangements between the tribes and federal government. The second section then focuses on the political economy and legislative changes associated with land transfers ? to examine the mechanisms of expropriation. The third section examines the impact of changes in and the uncertainty surrounding tribal water rights on western water use and quality. I use millions of observations of water pollution measurements from 1960 to the present to examine how the timing of lawsuits and specific settlements and rulings in these cases influenced water pollution patterns on reservations and outside reservations for surrounding waterways. The proposed project will thus enhance the current literature by using connecting new and existing historic information in novel ways to better understand the precursors and impacts of legal and economic institutions surrounding U.S. western settlement. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.