Jellico Mountain

Jellico Mountain is where I-75 crosses the Cumberland Mountains in Campbell County, Tennessee, just south of the Kentucky line. The interstate connects Jellico, TN (Exit 160, US 25W) with Williamsburg, KY to the north, and it ties the Knoxville area and the Caryville/LaFollette corridor into southeastern Kentucky toward Corbin. The ridge is geologically part of Pine Mountain, but locally everyone just calls the I-75 crossing Jellico Mountain.

This is the highest point on I-75 anywhere along its run from Florida to Michigan, sitting at more than 2,000 feet, and the interstate stays up in the peak area for roughly 8 miles (Wikipedia, Interstate 75 in Tennessee). The grade is documented at 6% (The Buzz, 2021 University of Memphis study, TDOT-advised). Northbound is the long climb, with a truck climbing lane added for the final pull that ends at the summit. Southbound is the long descent, and that is the direction where brake heat and runaway trucks are the worry.

What makes the mountain hard is the weather stacked on top of the grade. Dense fog rolls in often, the slopes are rockslide-prone, and winter brings snow, ice, and high winds. TDOT and the researchers who studied the corridor describe it as one of the most hazardous stretches of I-75 in Tennessee, known for a high crash rate tied to weather and grade. If you run this road, slow down through the fog zone, watch your brakes on the descent, and check conditions before you go.

• Highest point on all of I-75, Florida to Michigan, at more than 2,000 ft, with the interstate up in the peak area for about 8 miles (Wikipedia, Interstate 75 in Tennessee)
• Grade is documented at 6%; secondary trucking sources call it roughly a 5-mile descent (The Buzz 2021 study; 4RoadService)
• Northbound climb adds a truck climbing lane that ends at the summit; southbound is the long descent where brake heat is the concern
• Tennessee has no mandatory chain law: under TN Code 55-9-106, tire chains are permissive, not required (Tennessee Code 55-9-106 via FindLaw)
• Worst crashes cluster around mile markers 155 to 159, where fog and ice combine with the grade
• The low-visibility fog zone runs 4.4 miles between Exit 156 (Rarity Mountain Rd) and Exit 160 (US 25W), posted 65 mph (The Buzz 2021 study)
• NWS Morristown (MRX) issues the fog, wind, and winter advisories for Campbell County (NWS Morristown CWA)

There is no chain-control season on Jellico Mountain, because Tennessee does not run a western-style chain program at all. Under Tennessee Code 55-9-106, tire chains are permissive: you may use them when snow, ice, or similar conditions could cause your vehicle to skid, but nobody requires them and nobody turns you around at a chain-up station. There are no chain-control levels, no posted chain season, and no verified named chain-up or brake-check areas on the mountain. Closures here are incident-driven instead. When a crash, snow and ice, dense fog, or a rockslide hits, TDOT and the Tennessee Highway Patrol shut lanes or the whole interstate as needed, and they reopen it once the road is clear. There is no published wind or temperature number that automatically closes the mountain.

Work on the I-75 section that includes Jellico Mountain started in 1963, and the section was dedicated and opened to traffic on October 22, 1968 (Wikipedia, Interstate 75 in Tennessee). It was one of the most laborious and expensive Tennessee highway jobs of its time because of how much earth and rock had to be blasted and moved to get the interstate over the ridge. Before I-75 existed, north-south traffic between Caryville and Jellico used US 25W through the mountains. That old route still matters today, because when the interstate closes, traffic diverts back onto 25W.

The mountain keeps a record of slope trouble. In 2012 an earthen embankment under the highway near the Stinking Creek exit (about mile marker 144) began sliding, and TDOT had to run two-way traffic on the northbound lanes using crossovers (AARoads forum). On February 24, 2016 a rockslide hit the northbound lanes near mile marker 141.5, and TDOT closed I-75 between Exit 141 and Exit 160 for weeks. The agency awarded a $2.9 million emergency repair contract on February 29, 2016, with southbound lanes due to reopen within 14 days and northbound within 21, and trucks were detoured the long way around via Exit 29 at Corbin, KY to US 25E and TN-63 (WKYT and WYMT, 2016).