Big Thunder Mountain Railroad is an excellent roller coaster in Frontierland and one of the best attractions at Disneyland. The minimum height to ride is 40 inches.
This relatively mild coaster takes you through an abandoned gold mine in the old west. Try the "goat trick," by keeping your eyes on the goat as you descend the second hill for as long as you can. How mild is this coaster? The front cars of the train will bottom out on the third hill before the middle of the train even crests. A 2014 refurbishment added an "explosive" new surprise to that hill, though.
With a max speed of something like 35 mph, BTMR isn't going to scare anyone, but the attention to detail along the course of the track should be eye-popping to everyone. BTMR is a fun coaster for the whole family, especially a night when the ride seems to have a bit more zip. On the downside, BTMR does seem to slow down too much from time to time and just when it gets going nice and quick with a few real fun turns...it's over. Still, an excellent way to pass the time while waiting on your Star Wars Galaxy' Edge fastpasses!