We provide novel estimates of the location, timing, magnitude, and determinants of the start of the last U.S. housing boom. The last housing cycle cannot be interpreted as a single, national event, as different markets began to boom across a decade-long period, some of them multiple times. A fundamental factor, income of prospective buyers, can account for half of the initial jump in price growth, while expansion of purchases by underrepresented minorities cannot. The start of the boom also was financed conventionally, not by subprime mortgages. The latter's share did rise sharply over time, but only after a multi-year lag.