SR 3 begins at the junction with SR 36 south of the town of Peanut in Trinity County. SR 3 is also known as Bramlot Road from its southern terminus to Hayfork. This stretch of road through the Shasta-Trinity National Forest parallels the Hayfork River. Once SR 3 reaches the town of Hayfork, it travels along Hyampom Road east and snakes through the mountains to Douglas City and the junction with SR 299. From there, SR 3 runs concurrently with SR 299 north to the town of Weaverville. SR 3 then separates from SR 299, providing access to the Whiskeytown-Shasta-Trinity National Recreation Area and Trinity Dam along Lewiston Lake.