Crystal Cave Road (the former Colony Mill Road) and Crystal Cave

Crystal Cave Road is an approximately 6.5-mile highway which accesses the namesake cave in Sequoia National Park. Much of this corridor is comprised of a segment of the Colony Mill Road which was extended to the Giant Forest in 1903. The namesake Crystal Cave was discovered by U.S. Army members on a fishing trip in 1918. The cave was made accessible to the public when the Crystal Cave Road and Trail were constructed between 1939-1941.

Crystal Cave Road was heavily damaged during the 2021 KNP Complex Fire. The highway would reopen in May 2025 after removal of 4,800 dead trees.

Part 1; the history of the Colony Mill Road and Crystal Cave

In 1886 the Kaweah Colony was established along the North Fork Kaweah River. The Kaweah Colony's economy was based on logging which led to the construction of the first 18 miles of what was known as the Colony Mill Road. The Colony Mill Road and Kaweah Colony sought to harvest timber from the Redwood Sequoia Trees of the Giant Forest. The alarm raised by conservationists at the prospect of the Kaweah Colony harvesting the Giant Forest played a large part in the creation of Sequoia National Park in September of 1890. In October of 1890 General Grant National Park was created to the north around the Grant Grove of Giant Redwood Sequoias.

Subsequent to the creation of Sequoia National Park all logging operations within the park boundaries were terminated. The Kaweah Colony continued lumber operations outside the National Park Boundary but ultimately the logging operation was shuttered in 1892. This led to the Colony Mill Road largely being abandoned despite it being well engineered with an 8% grade that was constructed with the prospect of a railroad in mind. In 1903 the Colony Mill Road was extended by 8 miles into the Giant Forest by the U.S. Army to facilitate wagon travel into Sequoia National Park.

In 1905 Sequoia National Park ceded some of the water rights of the Kaweah River watershed to the Mount Whitney Power Company. In exchange the Mount Whitney Power Company would improve the Colony Mill Road in addition to building better roadway access to the Giant Forest. The yield of the construction by the Mount Whitney Power Company was the Middle Fork Road which later became a central feature of the alignment of the Generals Highway. By 1913 a roadway had been constructed to Wolverton to the north of the Giant Forest.

In 1918 what is now Crystal Cave was discovered by U.S. Army Calvary members Alex Medley and Cash Webster while on a fishing trip on Cascade Creek. The cave was initially known as "Hidden Cave" but was later renamed to "Crystal Cave" by Sequoia National Park Commissioner Walter Fry. The cave was closed to the public in 1919 following reports of vandalism.

During the 1919 Third State Highway Bond Act Legislative Route 10 was extended east from Visalia to the Colony Mill Road of Sequoia National Park. The Colony Mill Road ascending to the Giant Forest of Sequoia National Park from the eastern terminus of LRN 10 at Three Rivers can be seen on a 1919 Tulare County Road Atlas.

Starting in 1921 traffic headed to the Giant Forest would make a one-way ascent on the Colony Mill Road and a one-way descent on the Middle Fork Road (this is disputed in Tulare County history circles). From 1921 to 1926 Tulare County improved the Colony Mill Road and Middle Fork Road for better automotive travel. Traffic heading down the Middle Fork Road would cross the Kaweah River at the confluence of the East Fork Kaweah River and Middle Fork Kaweah River via the 1922 Pumpkin Hollow Bridge. The Pumpkin Hollow Bridge can be seen in this sketch below (from this Library of Congress article) with an incorrect completion date of 1924. The Pumpkin Hollow Bridge is now part of California State Route 198.

Beginning in 1926 construction of a new highway to connect Grant Grove of General Grant National Park south to the Giant Forest of Sequoia National Park began. Construction of the new highway heavily improved the Middle Fork Road which allowed for two-way traffic and negated the need to use the Colony Mill Road. In 1935 the Generals Highway was completed, and a dedication ceremony was held on June 23rd. Much of the information as described above was taken to the National Park Service article "When Two Parks Meet; History of the Generals Highway."

The 1935 Division of Highways Map of Tulare County shows the partially completed Generals Highway. Note: The Colony Mill Road is shown to be a somewhat well-traveled County Highway despite the improvements to the Middle Fork Road.

Beginning in 1939 the Civilian Conservation Corps would build a new roadway west of the Colony Mill Road to a trail linking to Crystal Cave. The Crystal Cave Trail was opened to the public via guided tours in 1940. The Crystal Cave Road and Trail wouldn't be fully completed until 1941.

The Crystal Cave Road can be seen extending west of the Colony Mill Road (the junction is at the blue pin) near the Marble Fork Kaweah River to the Crystal Cave Trailhead on the 1956 United States Geological Survey map of the Giant Forest.

At some point after the 1950s the Colony Mill Road between Crystal Cave Road west to the Sequoia National Park boundary was closed to traffic. The Crystal Cave Road designation was extended east to Generals Highway within the National Park Service jurisdiction. The portion owned by Tulare County is now known as North Fork Road and Tulare County Mountain Road 357.

Sequoia National Park would pave the trail inside Crystal Cave in 1985. This paving was part of an effort to mitigate dust which had begun to accumulate in the marble cave environment. Crystal Cave Road was severely damaged during the 2021 KNP Complex Fire. The National Park Service removed approximately 4,800 dead trees from the roadway and reopened it to traffic during May 2025.

Part 2; a drive on Crystal Cave Road and hike to Crystal Cave

Crystal Cave Road westbound splits from Generals Highway near the Four Guardsmen. Traffic is advised of a 22-foot vehicle length prohibition and is warned against stopping on the roadway due to falling tree hazards.

Crystal Cave Road descends to a bridge over the Marble Fork Kaweah River. This structure was completed in 1993 and mimics the aesthetic of several bridges on Generals Highway.

Below an undated photo from the Library of Congress displays a truss span which previously was located on the Colony Mill Road at the Marble Fork Kaweah River. This truss span was constructed in 1919 and was demolished in 1993.

Crystal Cave Road ascends from the Marble Fork Kaweah River and intersects the Colony Mill Trail. The old roadway is easy to identify due to a dirt grade being present, but the trailhead marker has not yet been replaced.

Crystal Cave Road terminates at the Crystal Cave Trailhead. Hikers are required to reserve a tour on one of the guided tours. The tours are intended to limit the number of people in the cave at one time and mitigate potential damage.