Boiling Springs is a census-designated place (CDP) in South Middleton Township, Cumberland County, Pennsylvania, and is part of the Harrisburg–Carlisle metropolitan statistical area.

[5] About 22 million US gallons (83,000,000 L) of water flows per day from a total of 30 springs dotted across approximately 2 acres (8,100 m2).

The impression of "boiling" does not result from the temperature of the water, which stays at 55.5–55.8 °F (13.1–13.2 °C) year-round,[5] but rather from a unique hydrogeological feature.

The cooler temperatures of the upper crust quickly solidified the hot rock, preventing it from reaching the surface.

This geological process created large, thin, subvertical sheets of impermeable basalt, or diabase dikes.

Much of the water, which has an acidic pH, is able to erode the valley's limestone bedrock and continue flowing at about 45 feet (14 m) below the soil.

Due to the positive pressure created by this confinement, water is pushed up to the surface and out of the artesian aquifer, giving the impression of "boiling" springs.

[5] A new model that has been proposed to account for these findings suggests that the excess water emanating from the springs originates from an area 60 km to the southeast on the southern side of South Mountain near the West Conewago Creek, Lat 40`04'56", long 76`43'13".

This 7-acre (2.8 ha) body of water was formed by partially damming the brook fed from 30 natural springs, including the "Bubble".

In the mid-18th century, a grist mill was built by Michael Ege on the southeast shore of the lake, to provide flour and grain for the iron works.

A picturesque, natural stone three-arch bridge, built in 1854, stands behind the mill, spanning the creek.

Where Children's Lake runs into the Yellow Breeches, a one-mile stretch of water known as "The Junction" provides quality catch-and-release fishing year round.

Hikers often mail themselves packages to pick up at the Boiling Springs Post Office, which is just feet from the trail.

Nearby Allenberry Resort Inn and Playhouse rents rooms to hikers for a reasonable rate.

The Carlisle Iron Works was in full production by the 1760s, and a grist mill was built at the end of the lake in 1762.

[12] Daniel Kaufman, who laid out the village of Boiling Springs in 1845, purchased 48 acres (19 ha) from his father, Abraham, in 1843.

Kaufman was sued by a Maryland slave owner in 1847 and convicted in Cumberland County,[13] but the verdict was overturned by the state Supreme Court.

Boiling Springs is now part of the Network to Freedom, a series of noteworthy sites along the Underground Railroad.

[12] The area around the lake was a recreation spot as early as 1875 when a steam launch began to operate to carry picnickers down the mill race to Island Grove, on Yellow Breeches Creek.

Recreation continues to bring people to Boiling Springs, ranging from fly-fishing on Yellow Breeches Creek to theater, dining and lodging at Allenberry Resort,[17] which opened in the summer of 1946.

Boiling Springs has an annual juried arts and crafts show, called Foundry Day,[19] on the first Saturday in June.