Oklahoma City has experienced significant population increases since the late 1990s. In May 2014, the U.S. Census announced Oklahoma City had an estimated population of 620,602 in 2014 and that it had grown 5.3 percent between April 2010 and June 2013. Since the official Census in 2000, Oklahoma City had grown 21 percent (a 114,470 raw increase) according to the Bureau estimates. The 2014 estimate of 620,602 is the largest population Oklahoma City has ever recorded. It is the first city in the state to record a population greater than 600,000 residents and the largest municipal population of the Great Plains region (OK, KS, NE, SD, ND).

When did the population increases begin in Oklahoma city?