Large-scale hydraulic mining for gold deposited in ancient gravel beds left pits along the river. Big nozzles called hydraulic giants shot powerful streams of water against a pre-historic river bed, now the bank of the stream, to expose and wash down gold-bearing gravel, which was then sluiced to recover the gold. This method was brought to Idaho in the 1860’s and remained in use until recent economic changes made gold mining unprofitable. Many pits, some enormously larger than this one, remain from those mining days.