 The mines were largely to the southwest of the town around Hollinwood and Werneth and provided enough coal to accelerate Oldham's rapid development at the centre of the cotton boom.At its height in the mid-19th century, when it was dominated by the Lees and Jones families, Oldham coal was mainly sourced from many small collieries whose lives varied from a few years to many decades, though two of the four largest collieries survived to nationalisation.In 1851, collieries employed over 2,000 men in Oldham, though the amount of coal in the town was somewhat overestimated however, and production began to decline even before that of the local spinning industry.