Glad to see that you're contemplating a trip on the Midland Trail!
Between Ashland and Charleston there isn't much to see, unless you are interested in archaeology. You can almost see the old route of the Midland Trail as you pass through Kenova, Ceredo, and Westmoreland on the way to Huntington. The old Midland Trail passed through Huntington mostly on 4th Avenue, then apparently went into Guayandotte and crossed the Guayandotte River before rejoining the present alignment of US 60. (This is according to my 1916 guide to the Midland Trail, reprinted in 1968.)
After you pass through Charleston there are a few interesting sites. The first you will come to is Malden, with Booker T. Washington's homeplace and his old church. Also, if you turn right instead of left at the first exit past Amherst, there is an old gasoline station with an interesting owner. I don't have his name right at hand, but he has some old gas pumps out front of his building, and he is restoring the old Greyhound bus that used to run along the Midland Trail in the 1930's. If he is there, and you ask nicely, he may open his garage to you. It is filled with historical vehicles, from an old early 20th century hearse to vehicles from the '20s to the '60s. He also has a great collection of Greyhound bus toys and models. He is a retired bus driver, if I remember correctly.
Further down the Midland Trail is Virginia's Chapel, a tiny church that was built by a father as a gift for his daughter. There are also historical gas and coal towns, and you will pass the Cannelton coal operation.
Soon you will arrive in Glen Ferris, with its historical hotel and some great views of the Great Kanawha River and the Falls of the Kanawha. This was the head of navigation from the Ohio River. You will also come to Gauley Bridge, which is the town at the junction of the Gauley and New Rivers, which join to form the Kanawha River. (Some say that the Kanawha should just be named the New River, since it is really just a continuance of that river.) Look to your left as you cross the Gauley River and you will see some deserted bridge piers out in the middle of the river. They date to the Civil War and the burning of the original bridge. At the time of writing of the 1916 guidebook you still had to cross the Gauley River by ferry.
Shortly after Gauley Bridge there is a waterfall on the left which is very picturesque, and after that the old road begins to climb the mountain. It is a scenic drive from Gauley Bridge to Hawks Nest, which is now a state park. The town of Anstead, in which Hawks Nest is located, has a lot of history, mostly related to the coal business. The town has developed a 4-mile (one way) walking trail that follows an old dinky line railroad that ran from the New River to Anstead. It is an easy grade and a scenic walk, with some old railroad relics still existing along the trail. There are also motels available in Anstead.
A historical site in Anstead is the old Halfway House, which is located on the original alignment of the Midland Trail. It is off to the left just after you pass through the modern town.
After Anstead it is only a few miles to Hico, and the junction with US 19. The New River Bridge is about six miles off to the left.
There is a lot of Civil War history along the Midland Trail between Gauley Bridge, Hawks Nest, and Lewisburg which is down in the valley of the Greenbrier River, near the Virginia Border. There is too much history to delve into here, but the battles of Cross Lanes and Carnifax Ferry were fought not too far from the Midland Trail.
Please feel free to contact me at firstname.lastname@example.org to discuss you trip further!