Mammoth Spring was a natural spring in York Township, DuPage County, Illinois, near present-day Oak Brook and Elmhurst. Reportedly appearing suddenly in 1861 on the Talmadge family farm, it first served irrigation and later became a crucial water source through a wooden conduit built in 1889 along Spring Road. Until 1916, before the source was depleted, it supplied all of Elmhurst’s water and part of Oak Brook’s, and it also supported the local ice trade through the Mammoth Spring Ice Company and Ice House at Fullersburg. Its practical importance declined in the early 20th century, but it remained significant in local development and place names.