Yellowstone Caldera Chronicles is a weekly column written by scientists and collaborators of the Yellowstone Volcano Observatory. This week's contribution is from Annie Carlson, Research Coordinator at the Yellowstone Center for Resources, Yellowstone National Park

Parks are for the people.

As the first national park, Yellowstone was established in 1872 as a “pleasuring-ground for the benefit and enjoyment of the people.” The National Park Service is tasked with both protecting park resources and providing for their enjoyment. To accomplish this dual mission, some infrastructure is necessary to support high levels of visitation. But how much infrastructure is appropriate?

How do you allow people to enjoy their parks without damaging resources? These questions continue to be a central focus for park managers, and our opinion of what is appropriate has changed over time. The Upper Geyser Basin, home of beloved Old Faithful Geyser, is a great place to ponder these changing attitudes.

Since the early days of the park, the Upper Geyser Basin has been one of the most popular areas for Yellowstone visitors. Today, you’ll find large parking lots, three hotels, two general stores, two gas stations, a visitor center, and a system of trails and boardwalks to safely navigate the thermal area.

But what you see today is only a snapshot of the infrastructure that has been there since the 1870s. In the past, structures have included tent camps, a bear-feeding platform, a thermally heated greenhouse, and even a hot-water swimming pool!

Old Faithful Inn, swimming pool, and store, with Beehive Geyser in the foreground, in 1921/Archives

This was not your average heated pool. The hot water was actually supplied by Solitary Geyser, a thermal feature nearly half a mile away from the pool.

In 1914, Henry J. Brothers received permission to build a bathhouse and to pipe hot water from Solitary. Visitors enjoyed the relaxing warm pool and unique setting (for a price, of course). The 1920 park regulations stated, “Henry J. Brothers operates a pool bathhouse at Upper Geyser Basin. Rates, 50 cents in large pool, $1 in private pool.”

In 1933, prominent park concessioner Charles A. Hamilton bought the Brothers bathhouse and remodeled it into a huge log building. The large indoor pool could hold 135 people and included a 25-foot-high lifeguard tower. Due to public health concerns and shifting attitudes, the geyser bathhouse was removed from the Upper Geyser Basin in 1951. However, some impacts have persisted.

As you can imagine, decades of piping hot water changed Solitary Geyser’s natural behavior. When the Brothers pool was built, they dredged and deepened the outlet channel. They also built wooden cooling frames to move the water downhill. The lowered water level in the spring allowed boiling to occur at depth, and Solitary Geyser began regular eruptive behavior.

Hot water was piped from Solitary Geyser to the former site of the geyser bathhouse.

Even though the water level has been restored since the bathhouse closed, Solitary continues to have regular geyser eruptions. You are likely to catch an eruption if you wait for 5-10 minutes, although most are only about 3 feet high.

The interior of the Hamilton bathhouse in 1939/Archives

At the time of the bathhouse, park managers and concessionaires deemed it appropriate to alter a geyser to provide the luxury of a swimming pool.

Through shifting public opinion and official policy, Yellowstone’s thermal features are no longer utilized in this way. They are valued for their natural beauty and fascinating thermophilic communities. Undoubtedly, attitudes and policy will continue to shift in the future along with a changing society. What current park practices might be phased out in the future, and what new practices will evolve?