The Opportunity Atlas is an initial release of social mobility data, the result of a collaboration between researchers at the Census Bureau, Harvard University, and Brown University. While the estimates in the Opportunity Atlas are not provisional, we are still testing aspects of the research product, including census.gov integration, planned annual data refreshes, and variable additions. Any opinions and conclusions expressed herein are those of the authors and do not necessarily reflect the views of the U.S. Census Bureau. All results have been reviewed to ensure that no confidential information is disclosed. The statistical summaries reported in this paper have been cleared by the Census Bureau's Disclosure Review Board release authorization number CBDRB-FY18-319.