Hidden Valley is located directly above the town of Estes Park in the state of Colorado. The ski area was around 1.5 hours southwest of Fort Collins, and sat close to 2 hours northwest of the Denver metropolitan area.

Downhill skiing at Hidden Valley can be traced back to the early 1900s. In 1916, the Estes Park Outdoor Club was established to promote outdoor recreation activity to the town of Estes Park. Starting in 1916, the club organized ski trips to Hidden Valley, having apparently taken much inspiration from Swiss guides. In 1925, the Estes Park Outdoor Club organized a new dedicated ski club affiliated with the National Ski Association. Downhill skiing continued throughout the 1920s and 1930s, with the club organizing frequent trips to the mountain and hosting many ski competitions. There was essentially no infrastructure, minus the access road, and the ski club operated on the upper mountain the entire time.

In 1940, the first cut trail on the lower mountain opened, dubbed Beginner's Paradise. In 1942, the first rope tow began operations on the upper mountain. In 1947, a rope tow on the upper mountain opened that featured wooden portal towers. This lift provided a quick and easy ride up the high alpine bowl terrain, and marks the beginning of Hidden Valley's golden years. These years were marked by significant capital investments, rising skier numbers, and prominence in the Colorado ski market. Several more trails on the lower mountain were cut, and another rope tow was added.

In February of 1953, a proposal was tabled to Congress that sought approval and financing for the construction of a new double chairlift, estimated at around $300,000. This proposal also sought additional improvements, including an 8,000-foot ski jump. Proprietors of the plan stated that these improvements would elevate Hidden Valley to the prestigious level of mountains like Sun Valley. The development proposal was mostly praised by various government officials, who stated that other Colorado mountains had been experiencing severe crowding. Federal officials took their time to study the plan, noting that the improvements would be considered, but that nothing would displace the natural beauties of the park.

By February of 1954, the federal government announced that they would relax National Park development regulations to pave the way for Hidden Valley's development. That summer, funds of $130,000 were allotted to the development of the mountain. Work immediately started on the construction of a 500-car parking lot, a bus turnaround, a snowshed tunnel, shuttle buses for skiers traveling between the lower and upper mountains, and additional rope tows. The ski operation was leased by the National Park Service to George Hertz, a local concessionaire, who ran the ski area until the early 1970s.

Hidden Valley experienced a surge in popularity that year, attracting record numbers. By the summer of 1955, two Von Roll platter lifts from Austria were ordered for both the upper and lower mountains. Construction on the ski lodge was started in 1955. Unfortunately, logistical problems delayed the opening of the platter lifts until the following year.

Following the lift improvements, more money was invested into maintaining the access road, which helped improve accessibility. However, poor early season snow conditions plagued Hidden Valley, especially affecting the lower mountain. Despite the poor snow, by 1959 Hidden Valley was operating 5 days a week with respectable skier numbers.

In May of 1960, the National Park Service again put forth suggestions for improvements, including the replacement of both the Von Roll platter lifts with T-bars. By July, the National Park Service green-lit these improvements, allocating $80,000. Over the next few years, the platter lifts were completely rebuilt into T-bars. A new beginner run was also cleared on the lower mountain, with a new rope tow added. One of the platter lifts was relocated to Cutara Basin, and the remains still sit on the mountain.

Hidden Valley continued on in the 1960s, enjoying popularity from mostly local skiers. While early seasons were fairly consistently devoid of snow, the ski area did experience some very late closures, mostly thanks to the upper mountain terrain. By 1967, very limited snowmaking was installed at lower Hidden Valley in an attempt to combat the chronic lack of snow. In 1968 and 1969, the ski area installed two beginner Poma platter lifts, which replaced rope tows. This area was located on the lower mountain, and was likely where the snowmaking was used. Additionally, the Aspen ski run was extended and the lower mountain ski lodge was expanded.

The 1969-70 ski season went on to become Hidden Valley's best ever in terms of attendance. This led Hidden Valley, in the summer of 1971, to install a brand new Heron Poma double chairlift. This lift ran from the lower mountain base to the upper mountain on Trail Ridge Road, effectively uniting both mountains and improving the lappability of several runs. That being said, the lift was very long and it effectively sat in a wind tunnel. Reportedly the ride up was absolutely miserable, and many skiers only rode the lift several times a day. This chairlift came during a time of increased expansion at many Colorado ski resorts. Hidden Valley also changed its name to Ski Estes Park in 1972.

Despite the improvements, in 1973 the US Park Service proposed to phase out the ski area in the next two decades. This came after a new master plan for Rocky Mountain National Park was adopted, emphasizing wilderness preservation. According to the park superintendent at the time, Hidden Valley was not so hidden, and was seen as a blight on the pristine wilderness. The ski area ran on 20-year leases, and the last lease was signed in 1971. The park indicated that the ski hill would be gradually phased out until closure in 1991. This plan was not well received by the local skiing community, but it was ultimately passed through.

The new master plan also coincided with a shift in skier habits. In 1973, the Eisenhower Tunnel opened on I-70, which significantly cut down driving time between Denver and many well-developed Summit County ski resorts. Hidden Valley, which was tucked away in a region that suffered from snow shortages, began to struggle. By early 1976, reports circled that indicated the National Park Service might purchase the mountain.

Later on in 1976, Rocky Mountain National Park officially purchased all Hidden Valley assets from George Hertz. The park indicated that they would operate the mountain for the time being, but would gradually phase it out. Citing safety concerns, the park announced that the chairlift would be removed and that shuttle buses would fill the role. This chairlift was officially removed by the 1978 ski season and sold to a ski hill in Canada.

The National Park Service transferred the daily operations of the ski area to the Estes Valley Recreation District, which was a separate entity though still linked to the National Park Service. Several key upgrades were undertaken. A new snowmaking pond was constructed and more efficient snow guns were purchased. Additionally, a skating rink was built where the chairlift used to load. The park service announced that price increases would freeze, and that they would try to keep the ski area open for as long as possible during the season.

Throughout the 1980s, Ski Estes Park held the line on affordability. In 1985, a new Dopplemayr T-bar replaced the ancient upper mountain lift. Apart from that improvement, nothing much changed. The ski area competed with other National Park Service assets for funding, and when it did receive funding, most of that capital went into upkeep. Deferred maintenance continued to grow, and the ski area ran as it always had.

The 1989-90 ski season was one of the worst ever for Hidden Valley. A lack of snow forced the resort to announce that it would not be able to operate at all. National Park officials considered permanently closing the mountain, citing losses of around $150,000. Despite two private bids to the National Park Service to manage the ski hill, the park was pretty adamant that the ski area was over.

A group called Friends of Ski Estes Park was formed, and they pledged to raise capital to keep the ski area open. During the summer of 1990, the group fundraised over $100,000. Additionally, the district added $50,000 and the town of Estes Park contributed $40,000 towards the group's efforts. The citizens group attempted to file a new permit application for Hidden Valley. However, it was quickly denied by the Park Service. In the denial, the Park Service noted that the Friends of Ski Estes Park lacked prior experience in ski area management. They also noted that the group missed a $25,000 deposit to the district.

And thus, officially by 1991, downhill skiing operations at Hidden Valley came to an end. All equipment was removed. The ski lifts were sold to Vail Mountain, where some continue to operate to this day. The lodge was demolished in 2002. Although downhill skiing is no longer a part of Hidden Valley, many of the ski runs are still clear, and it remains a popular winter spot for enthusiasts. Despite the popularity, there is virtually no chance that Hidden Valley would ever come back as a downhill ski area.