Midway Geyser Basin

Overview

Midway Geyser Basin sits between the Upper and Lower Geyser Basins along the Firehole River and is one of the park’s most visited stops. A compact boardwalk loop carries you over the river and through a tight cluster of headline hydrothermal features—fast, dramatic, and easy to experience.

What You’ll See

• Grand Prismatic Spring: roughly 370 feet across—longer than a football field—with a near‑boiling deep‑blue center rimmed by orange, yellow, and green microbial mats.
• Excelsior Geyser Crater: a huge, steaming crater (about 200 x 300 feet) that discharges thousands of gallons of hot water per minute into the Firehole River.
• Opal Pool and Turquoise Pool: smaller springs that add eye‑candy color to the loop.

History & Research Notes

Trappers documented a “boiling lake” here as early as 1839. In 1871, geologist Ferdinand Hayden dubbed it “Prismatic” for its colors. In the 1990s, park geologist Rick Hutchinson used a small research boat—the “Little Dipper”—to take measurements and even remove litter from Grand Prismatic’s center. Soundings suggested the spring exceeds 120 feet deep, though the exact depth remains uncertain.

Geology & Color

Yellowstone’s hydrothermal features are the surface expression of a vast volcanic system. At Grand Prismatic, heat‑loving microbes thrive in temperature bands, painting those signature rings of orange, yellow, and green around the blue hot core.

Best Time to Visit

• Crowds: This lot is a known bottleneck. Arrive early or come after late afternoon to avoid peak tour‑bus crunch.
• Lighting and visibility: Midday sun brings out the strongest colors. Cool mornings can be steamy (fewer people but more obscured views). Wind helps strip steam for clearer looks.
• Quick logistics: The boardwalk loop is about 0.8 miles. Midway is about 5.9 miles north of the Old Faithful Interchange or 10.2 miles south of Madison Junction on the Grand Loop Road.

Views & Photography

From the boardwalk, you’re at ground level, so the spring’s full rainbow bands can be muted by steam. For the iconic elevated perspective, take the Fairy Falls trail to the Grand Prismatic overlook (about 0.5 miles to the viewpoint).

Wildlife & Safety

Bison and other animals occasionally pass near the boardwalks—give them space. Stay on the boardwalks; the ground is thin and the water can scald. Don’t toss coins or objects—litter has had to be removed from these features.