For humans who can survive an acceleration of about 3 g, you'd need a 1000 km long railgun in order to deliver enough energy.
For cargo a railgun a few miles long would probably be enough, but designing a missile which can survive surface air densities while travelling at orbital velocities would be very difficult.
Launching bulk cargo would still be a very worthwhile thing to do. Solar power satellites, anyone? The main obstacle is the launch cost. If we could reduce the shipment of bulk items to orbit to freight rates, then solar power satellites would become a reality. The US military already has specs for electronic components that can withstand 100,000 gravities. (Yes, the number of zeroes is correct!) I bet we could develop lightweight thin-film solar panels that could be rolled up and packaged to survive 1000.
For cargo a railgun a few miles long would probably be enough, but designing a missile which can survive surface air densities while travelling at orbital velocities would be very difficult.