In this article, authors Robert Warren and John Robert Warren describe a method for producing annual estimates of the unauthorized immigrant population in the United Sates and components of population change, for each state and DC, for 1990–2010. The authors quantify a sharp drop in the number of unauthorized immigrants arriving since 2000, and they demonstrate the role of departures from the population (emigration, adjustment to legal status, removal by the Department of Homeland Security [DHS], and deaths) in reducing population growth from one million in 2000 to population losses in 2008 and 2009. The number arriving in the U.S. peaked at more than one million in 1999–2001 and then declined rapidly through 2009. The authors provide evidence that population growth stopped after 2007 primarily because entries declined and not because emigration increased during the economic crisis. The authors’ estimates of the total unauthorized immigrant population in the U.S. and in the top ten states are comparable to those produced by DHS and the Pew Hispanic Center. However, their data and methods produce estimates with smaller ranges of sampling error.