Grand Prismatic Spring

State: Wyoming, within Yellowstone National Park's Midway Geyser Basin. Type: hot spring, approximately 370 feet (110 m) in diameter and 160 feet (50 m) deep, per Wikipedia. The largest hot spring in Yellowstone and the third-largest in the world, behind Frying Pan Lake (New Zealand) and Boiling Lake (Dominica). Discharges an estimated 560 US gallons of 160-degree-F water per minute. First noted by trappers in 1839; formally named by the 1871 Hayden Geological Survey.

Grand Prismatic Spring is Yellowstone National Park's largest hot spring and one of its most photographed features, located in the Midway Geyser Basin along the Grand Loop Road between Old Faithful and Madison. Measuring roughly 370 feet across and 160 feet deep, it ranks as the third-largest hot spring in the world. Its striking rainbow coloration comes from two sources: the sterile, deep blue center reflects the intrinsic color of clear water, while the vivid orange, yellow and green rings around the edges are produced by heat-loving microorganisms called thermophiles, whose pigmentation shifts with the seasons, more orange-red in summer and darker green in winter. The spring discharges an estimated 560 gallons per minute of water around 160 degrees Fahrenheit. First noted by fur trappers passing through the area in 1839, it was formally described and named for its prism-like colors by geologists on the 1871 Hayden Geological Survey, one of the expeditions whose reports helped persuade Congress to establish Yellowstone as a national park the following year.

Grand Prismatic Spring sits in the Midway Geyser Basin of Yellowstone National Park, along the Grand Loop Road roughly midway between the Old Faithful area and Madison Junction, in the park's south-central section.

Like the rest of Yellowstone's high plateau, the Midway Geyser Basin has a cool mountain climate with short summers and long, snowy winters; the intense steam plume rising from the spring is especially dramatic against cold winter air, though the surrounding boardwalks and overlook trail are only accessible via guided snowcoach or snowmobile once regular roads close for the season.

Midday sun generally gives the clearest view of the spring's colors from ground-level boardwalks, since steam can obscure the view in cooler morning air; the elevated Grand Prismatic Spring Overlook Trail helps visitors see the full pattern of colors from above the steam. Visiting outside the busiest midsummer hours (early morning or later afternoon) can reduce crowding on the parking areas and boardwalks.

Fur trappers passing through the Yellowstone region noted the spring as early as 1839, well before organized scientific survey. The 1871 Hayden Geological Survey, one of the expeditions that documented Yellowstone's geothermal wonders in the years leading up to the park's 1872 establishment, formally named the feature Grand Prismatic Spring for its striking, prism-like coloration. Its scientific and public interest has grown since, both for its microbiology, the thermophilic organisms responsible for its coloring, and as one of the most recognizable images associated with Yellowstone.

Visitors walk the boardwalk trail through the Midway Geyser Basin for close-up views of the spring's colors and steam, and many also hike the Grand Prismatic Spring Overlook Trail, a short uphill trail on the opposite side of the basin that offers an elevated view showing the full rainbow pattern from above. Photography is a major draw, particularly from the overlook.

Within the Midway Geyser Basin, Grand Prismatic Spring is the centerpiece, but the basin also contains Excelsior Geyser Crater, another large thermal feature, along the same boardwalk loop. The nearby Fairy Falls trailhead area connects to the overlook trail.

Grand Prismatic Spring is reached via the Grand Loop Road in Yellowstone's south-central section, with a dedicated parking area for the Midway Geyser Basin boardwalk and a separate trailhead nearby for the overlook trail; both are reachable only when the surrounding Grand Loop Road segment is open to regular vehicles (per NPS road-access data, generally mid-April through October).

The spring itself is visible year-round as a natural feature, but vehicle access to the parking area follows Yellowstone's seasonal road schedule, generally open mid-April through October and closed to regular cars in winter. Boardwalks are typically accessible during daylight hours when the road is open; confirm current seasonal access on nps.gov/yell.

There is no separate fee to view Grand Prismatic Spring beyond the standard Yellowstone National Park entrance fee ($35 per vehicle for 7 days, per NPS), since it sits inside the park.

Allow 30 minutes to an hour for the Midway Geyser Basin boardwalk loop, plus an additional 30-45 minutes if hiking the Grand Prismatic Spring Overlook Trail for the elevated view.

There is no lodging directly at Midway Geyser Basin; the nearest in-park accommodations are at Old Faithful, a short drive south, with additional options in gateway towns such as West Yellowstone, Montana.

No dining is available directly at the spring; the nearest in-park food service is at Old Faithful's developed area a short drive away, with a broader range of restaurants in gateway towns like West Yellowstone.

Old Faithful and the Upper Geyser Basin are a short drive south along the Grand Loop Road and commonly paired with a Grand Prismatic Spring visit on the same day. Excelsior Geyser Crater sits within the same Midway Geyser Basin boardwalk loop.

Yellowstone Airport in West Yellowstone, Montana (seasonal) is among the closest airports via the park's West Entrance; Jackson Hole Airport serves visitors approaching via the South Entrance. A rental car is the standard way to reach the site from either.

Stay strictly on the boardwalks; the ground around the spring is thin and the water is scalding, and stepping off the walkway has caused serious injuries and deaths at Yellowstone's thermal features historically. Watch footing on the overlook trail, which involves an uphill hike, and keep a safe distance from any wildlife encountered along the way.

Sturdy footwear for the overlook trail's uphill hike, a hat and sun protection for exposed boardwalk sections, water, and a camera, since midday light and the overlook's elevated view give the best photo opportunities.

Arrive early or later in the day to find easier parking at the popular Midway Geyser Basin lot, which fills quickly in summer. Combine the visit with the Grand Prismatic Spring Overlook Trail for a view that shows the full pattern of colors, which is hard to appreciate from the boardwalk alone since steam often obscures ground-level views. Pairing this stop with nearby Old Faithful makes for an efficient half-day itinerary.

Dial 911 for any emergency within Yellowstone. The park's general visitor information line is 307-344-7381.

Yellowstone National Park - Midway Geyser Basin (National Park Service) - https://www.nps.gov/yell/index.htm

This section is being updated and will be available shortly.

This section is being updated and will be available shortly.

This section is being updated and will be available shortly.