upwards-curving folds in the caprock called anticlines, or sometimes an inversion of an anticline called a syncline, greatly varied the depth of the reservoirs, from around to just beneath the surface. The majority of the oil wells in the vicinity of Pithole and the Oil Creek valley tapped into a sandstone formation known as the Venango Third sand. The Venango Third contained large volumes of oil under high pressure at only below ground level. Other oil-producing formations in the area were "the Venango First and Second [sands], the latter often prevailing after the Third sand was lost." At Pithole, the "first sandstone was reached at , the second at , the third at , the fourth at , and the oil itself at " by the Frazier Well, according to a report by the Oil City Register. Inaccurate numbering of the layers by the drillers, however, put the Fourth sand above the real Third at . Geography and climate Pithole is located in northwestern Pennsylvania, southeast of Erie and north-northeast of Pittsburgh. The nearest cities to Pithole are Titusville, approximately to the northwest, and Oil City, to the southwest. Pithole is located on Pithole Road (State Route 1006), almost southwest of Pennsylvania Route 36 and about east Pennsylvania Route 227. Pithole was laid out with four primary east–west streets: First, Second, Third and Fourth. Duncan, Mason, Prather, Brown and Holmden Streets traversed Pithole from north to south. Each street was wide, except for Duncan at . All five north–south streets terminated at First Street; Mason started at Third; Prather and Brown started at Fourth. Duncan and Holmden Streets both began at a Y-intersection with the road from Titusville. All four east–west streets began at Duncan and ended at Holmden Street except for First, which extended to the Frazier Well. July is the hottest month in Pithole, when the average high temperature is and the average low is . January is the coldest month with an average high of and an average low of . The average of precipitation a year wreaked havoc on Pithole's many unpaved streets, especially the heavily traveled First and Holmden. Portions of First Street were planked or corduroyed in response to the resulting quagmire of mud that would often trap wagons and draft animals. History The area around Pithole, and modern-day Venango County, was formerly inhabited by Eries, who were eventually wiped out by the Iroquois