Placement Considerations
Rockets can most easily reach satellite orbits if launched near the equator in an easterly direction, as this maximizes use of the Earth's rotational speed (465 m/s). Such launches also give a good orientation for arriving at a geostationary orbit. For polar orbits and Molniya orbits this does not apply.
Altitude of the launch site is not a driving factor because most of the delta-v for a satellite launch is spent on achieving the required horizontal orbital speed. The small gains from a few kilometers of extra altitude at the start does not usually off-set the ground transport problems in mountainous terrain.
Many spaceports have been placed at existing military installations, such as intercontinental ballistic missile ranges, which is not always ideal for satellite launches.
A rocket launch site is built as far as possible away from major population centers in order to mitigate risk to bystanders should a rocket experience a catastrophic failure. In many cases a launch site is built close to major bodies of water to ensure that no components are shed over populated areas. Typically a spaceport site is large enough that, should a vehicle explode, it will not endanger human lives or adjacent launch pads.
Planned sites of spaceports for sub-orbital tourist spaceflight often make use of existing ground infrastructure, including runways. The nature of the local view from 100 km (62 mi) altitude is also a factor to consider.
Read more about this topic: Spaceport