The height would 4 miles 20,000 ft, the length of the run 81 miles. The location would likely be up a western slope of the Andes in South America, as close to the bulging equator and as far from the the center of the earth as possible. Launching to the East near the Equator takes advantage of maximum rotational velocity of the Earth’s surface.
an 81 mile space tube attached to the Andes would have to contend with earthquakes