SD: Standard Deviation; IQR: Interquartile range, the 25th to 75th percentiles. 
Rural and urban are defined using census tracts.

Sources: Data on services offered by each hospital came from the American Hospital Association Survey; data on demographic characteristics of census tracts came from the American Community Survey (2015-2019 estimates); data on persistent poverty came from the National Cancer Institute’s Surveillance, Epidemiology, and End Results (NCI SEER) file on time-dependent census tract attributes; and files used for mapping came from the National Historical Geographic Information System (NHGIS).