The road leading to the summit has a sign on the rightside of the entrance. It says "FAA En Route Radar Lynch, KY".
Also, the summit road is the PAVED road, not the dirt road next to it.
The USGS Benchmark disk for Black Mountain is found on a large boulder, just beyond a small path/opening in thick brush located on the east side of the summit area.
I observed no sign at the entrance to the Summit Road from Rte. 160 coming from Kentucky side, on a recent visit. But a turn to the right, just before the 'Welcome to Virginia' sign, leads to the Summit Road (uphill). The handsome plaque, marking the summit height (4,139 ft.) and honoring local World War II Veteran, and Cable TV pioneer William Risen, was erected on a pedestal by 'Hands Across the Mountains'. Directly beyond the plaque, the USGS Survey Marker lies on a prominent boulder in a small copse of trees. It was a foggy, early Fall evening with wildflowers in profusion; not a bad day in the beautiful Southern Appalachians.
I did this point last week. Here's some updates:
-The summit road is no longer "paved." Although remnants of pavement remain, the drive up is mostly dirt
-There is no sign for the summit road. However, the summit road is the road to the LEFT of the FAA Long Range Radar sign
-There is a large pullout right next to the "Welcome to Kentucky" sign. I slept in my car there the night before and this provides an alternative to camping miles away.
-Most importantly: Under NO circumstances attempt to go to the next town over (Lynch/Cumberland) by taking a "scenic adventure" using the other dirt roads in the area. I decided to do so and - going down Cloverlick Creek road from Black Mountain - encountered some SERIOUS grades and terrain. Since I was departing the highest point in the state, I could descend alright, but if I had to go up a similar road, I would seriously be at risk of having to abandon the car. If you're going to do a dirt road adventure, make SURE that you have a passable route and do prior research. Don't get into the situation I did