You can come in that way from Tellico Plains, that way is a pretty nice ride along the river. You can also cut across on Joe Brown Highway but beware, it is a highway in name only. I came across that way once and it was an experience with a trailer let me tell you but it brought me right into Crawfords. Another and better option is to go through Robbinsville and take the Cherohala Skyway toward Tellico Plains. You can cut off of the Skyway onto a Forest Service road that brings you out almost right at the State Line Campground.
Directions from Asheville, NC
From Asheville take I40W and take the Hwy 74/23/19 exit to Waynesville. Stay on 74/23. After you pass Bryson City go about 10 miles and turn right on Hwy 28 to Almond/Robbinsville just before you enter the Nantahala Gorge. Go about 10 miles, after you go through the community of Stecoah take a left on Hwy 143. You will come to a dead end with a traffic light in Robbinsville, big grocery store on your left. Take a right on Hwy 129/143. 3 or 4 miles out of town bear left on Hwy 143/Massey Branch Road. Stay on Hwy 143 toward Joyce Kilmer National Forest/Tellico Plains. 143 will take a hard left turn up hill at the turn off to Joyce Kilmer. This is well marked with a pull off, National Forest Sign, etc. From this point go EXACTLY 15 miles. This is a beautiful drive uphill almost all the way, when you pass elevations of 5000 feet you are getting close. You will pass several scenic pull offs. At the 15 mile mark you will pass a pull off that has restrooms, maybe the only one you will pass with a restroom. Take the NEXT small dirt road to the right, just before you get to a bridge/overpass, maybe 100 yards past the pull off. If you cross a bridge/overpass after the restroom/scenic pull off at the 15 mile mark you have gone too far! After a couple of hundred yards at a split in the road turn left back under the bridge on the Skyway. This should not be attempted at night unless you have been this way several times in the daylight. You will now be on a numbered forest service type gravel road/N River Rd. After about 7-8 miles downhill you will start to pass numbered FS campsites along the river. Take the first FS marked road to the left with a bridge over the creek, sign says to Green Cove. After about 4 miles you will dead end into River Road. Take a left and you will be about 5 miles from the State Line Campground. You can follow along with this route if you use the Google/Maps web site.
Directions from Murphy, NC
Take Tennessee St in downtown Murphy north across the bridge where it becomes Joe Brown Hwy (NC 1326). Follow Joe Brown Hwy 2.8 miles to the flashing caution light at Beaverdam Road. It comes up fast! Turn RIGHT onto Beaverdam Rd. and proceed 5.5 miles to Davis Creek Rd. Turn RIGHT onto Davis Creek Rd and follow it about 5 miles it to where it becomes Trail 1 (Forest Road 420-1) at Allen Gap. Stay on Trail 1 to get to State Line Campground. There are fee stations for the OHV area on Trail 1 at Allen Gap and just inside NC near the head of Trail 6.
Directions from Tellico Plains, TN
If you are in Tellico Plains, you are at or near the intersection of TN 68 and TN 165 (Cherohala Skyway). Turn onto TN 165 and proceed to the River Road (FR 420-1). Turn RIGHT onto River Road. The signs are marked Tellico Ranger Station, Bald River Falls, Tellico Hatchery, and Green Cove. Make no turns until you come to State Line Campground and you're there. You'll know you're right if you pass the Green Cove Motel and Store and the Tellico Lodge Store on the way in. OHV