Named after Valladolid, at the time the capital of Spain, the first Valladolid in Yucatán was established by Spanish Conquistador Francisco de Montejo's nephew on May 28, 1543 at some distance from the current town, at a lagoon called Chouac-Ha in the municipality of Tizimin. However, early Spanish settlers complained about the mosquitos and humidity at the original location, and petitioned to have the city moved further inland.

On March 24, 1545, Valladolid was relocated to its current location, built atop a Maya town called Zaci or Zaci-Val, whose buildings were dismantled to reuse the stones to build the Spanish colonial town. The following year the Maya people revolted, but were put down with additional Spanish troops coming from Mérida.

From wikipedia: http://en.wikipedia.org/wiki/Valladolid,_Yucatán