As it approaches the summit, the Middle Fork Smith River turns east, but US 199 continues northeast, following Griffin Creek to near its source (where there is a rest area), and passing under Hazel View Summit, the border between the Smith River NRA and the Rogue River-Siskiyou National Forest, in the 1963 Collier Tunnel (elevation about 2,100 ft or 640 m).

Upon leaving the tunnel, US 199 descends alongside the small Broken Kettle Creek into the Elk Valley and crosses into Oregon.

[2] US 199 leaves the national forest as it enters Oregon and descends into the Illinois Valley, passing O'Brien and the west end of OR 46 in Cave Junction.

North of Cave Junction, US 199 leaves the Illinois River, which curves west towards the ocean, and follows several small creeks past Selma to Hayes Hill Summit (elevation about 1,700 ft or 520 m).

The highway descends from the summit alongside Slate Creek past Wonder and Wilderville and ends up in the Rogue River Valley, where it enters Grants Pass.

[7] The older route through downtown is a one-way pair on Sixth (southbound) and Seventh (northbound) streets, entirely overlapping OR 99 to I-5 exit 58, where OR 99 continues with I-5 to the north.

The Crescent City and Yreka Plank and Turnpike Company was incorporated at a meeting on June 10, and a survey was completed in October, but work stopped with the Panic of 1855.

Gasquet also built a free road from Gasquet Flats along the Smith River to the mouth of the South Fork, including a suspension bridge across that waterway, and Del Norte County extended it along the Smith River and Mill Creek and over Howland Summit to the Crescent City Plank Road just east of Crescent City.

[20] By 1924, the road was part of the Redwood Highway, which continued south to Sausalito,[21] but was still completely unimproved between Crescent City and Waldo, Oregon.

[18]) A new highway between Gasquet and Kerby was completed by the two states in September 1926,[23] and in June 1929 the new Hiouchi Bridge over the Smith River was dedicated, bypassing the remainder of the old road over Howland Hill.

[25] One major improvement to the highway's alignment was made after 1929: the Collier Tunnel replaced the winding route over Hazel View Summit in California on July 20, 1963.