of the twentieth century. Sebastian de la Cruz, Valtierrilla's first mayor in 1733. He participated in the construction of the Chapel of the Holy Cross in 1724, asked the Viceroy elect Valtierrilla authorities. He participated in the land dispute over dispossessions carried out by Santamaria Nativitas, and achieved restitution of the land. Population In 1754, the population of Valtierrilla was 406 while Salamanca had 1508 inhabitants. By 1900, the Valtierrilla's population grew to 2016 people while Salamanca had risen to 13,583. According to the 2005 census, the county seat of Salamanca accounted for 61.57% of the total municipal population (143,838 inhabitants) and Valtierrilla accounted for 5.19% (12,118 inhabitants). In 2007 a further census reported a population of 13,200. History Pre-Hispanic times The earliest known human settlements in Valtierrilla are from the Chupicuaro culture and date from the Preclassic or Formative periods between 400 and 200 BCE. Semi-nomadic groups settled on the banks of the Lerma and Laja rivers in scattered villages with an egalitarian social structure. No remains of monuments or stone sculpture have been found, only surface alignments of rocks on top of the Cerro Prieto hill. At the end of 1985, a bridge over the River Laja was built so it could be crossed when the water is high and reach surrounding towns. The cluster of stones was collected for use in the masonry of the bridge, revealing the remains of a stone ceremonial pyramid or stepped structure, with a base about in diameter and a projected height of less than . It was built as a dry stone construction (i.e. using no mortar). Unfortunately, the rocks comprising the structure were removed, rather than preserved. The Chupicuaro abandoned the region for unknown reasons, though semi-nomadic groups in the region probably remained. The Aztecs probably passed through the area during their migration to the Valley of Mexico around the twelfth or thirteenth century but did not settle in the area. Before the Spanish arrived there were large groups of Indians, principally Chichimecas, Pames, and Guamares, on the banks of the Lerma and Laja. Colonial Era After the conquest, the Spanish began to make expeditions into the Chichimec region. On 4 May 1593, all titles and relegated residences were set to go to the sons of the conquistadors. Don Gaspar de Váldez took advantage of this situation to register the ranches of Mancera and Valtierra that currently occupy the region