From the trailhead at Forest Road 68, this is a 3 mile trail (6 r/t), however if you are connecting to the Indian Springs Trail #627 as I did as part of a two day trip, make sure to account for an extra 1/2 mile each way. Strangely, the sign for the West Fork Trail posted at the Indian Springs Trail junction says it's 3 miles to the Black River, but after hiking 1/2 a mile an reaching the roadside trailhead, signs there also say 3 miles...
The West Fork trail is a very enjoyable trail through dense Pine and Aspen forest for the first two miles, with a well maintained surface. It passes through two picturesque meadows, including one with what appeared to be the ruins of some kind of building. I did not investigate, but the Topo map indicated an old 4wd road just north of the meadow which would provide access to such a building.
The last mile of the trail becomes less pleasant to hike, getting rocky at times, and with loose footing in places. Luckily, once on this part of the trail, views of the river and lush valley below motivate easily.
The trail reaches the Black River at Deadman Crossing, which is named after Deadman Spring, which drains into the river at the same point. This is an excellent spot to rest and grab a bite to eat. Weekends will find occasional anglers along the river, and some backpackers will camp in this area as well.
The Thompson Trail #629 continues upstream from here, and is perhaps the most beautiful hike I've been on in the White Mountains. I highly recommend the extra 5 mile round trip. I've posted a trip log for that trail as well.
We camped near Deadman Crossing and enjoyed a light-rain thunderstorm in the evening, followed by a dry, cloudy night, keeping the temperatures in the upper 40s (it was in the low 30s on a clear night the day before).
The next morning, after 3 beautiful hours of light rain drizzling in this green river valley, we headed up the rocky slope and back toward the trailhead.
Though the trail is listed for hiking and mountain biking, I wouldn't recommend anybody to bike the last mile down to the river. Not worth the return trip.