County Fair Guide

Jefferson County Fair

Boulder, Montana

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2026 Dates

August 20–23, 2026

Duration

4 days

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Size

small

What to Expect

Expect livestock judging, 4-H competitions, carnival rides, and the working-class mining and ranching community spirit of the Silver Bow corridor.

About Jefferson County Fair

The Jefferson County Fair in Boulder is a four-day August celebration in the Jefferson River valley, serving the ranching and mining heritage communities between Helena and Butte.

Visitor Tips

Boulder is between Helena and Butte in the Jefferson River valley — the area's copper and silver mining legacy and the Elkhorn ghost town are distinctive local features.

Heading to Jefferson County Fair?

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