This research award will support the creation of the Big Microdata Network. Through multiple collections, researchers now have access to two billion census records describing the entire American population from the mid-nineteenth century to the present day. Although these data collections have rich research potential, the massive scale and scope of the data poses new challenges for researchers. The Network will address these challenges by building an open interdisciplinary community of researchers. It will connect these researchers through online communication and in-person meetings, including four annual research conferences. It will lower barriers to research by creating working groups to provide training and guidance. The Network also will conduct outreach to new community members, including annual training workshops. Outreach efforts will focus on scholars from underrepresented groups, early career scholars, and those outside major research institutions. The Network will directly contribute to the training of underrepresented graduate and undergraduate students through participation in the institution's Summer Diversity Fellowship program. Leveraging the broad experiences and expertise of the research community, the Network will attract new scholars to these valuable data resources, enabling new research.<br/><br/>The Big Microdata Network will support an emerging interdisciplinary community of scientists using vast collections of census microdata describing the American population from the mid-nineteenth century to the present day. It will leverage previous federal investment in massive census data collections which describe the American population. The IPUMS full-count census collection provides consistently coded data from 1850 to 1940 from census records that have been released publicly following the 72-year requirement. The Federal Statistical Research Data Centers provide access to decennial census data for 1960 to 2010 under appropriate data security measures. Some researchers, however, lack the computing power necessary to take advantage of these data, and even those with sufficient resources still require new programming strategies to manipulate and analyze data of this scale. Record linkage poses a host of problems, from analytic decisions to computational capacity. Investigators working to exploit geographic detail also face considerable startup costs for geocoding, developing GIS boundary files, and conceptualizing new geographic measures of neighbors and neighborhoods. Restrictions around data access pose constraints for sharing resources and present difficulties for data replication and preservation. By increasing access and lowering barriers to using these data, the Network will help researchers overcome these challenges. It will advance scholarship across a range of fields, including economics, sociology, demography, statistics, geography, epidemiology, urban planning, and public policy.<br/><br/>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.