Gate harvesting program
Taking months to complete, several teams were organized to search for unused Stargates in both galaxies. Stargates orbiting planets in Pegasus had a distinct advantage, because in absence of dial-home devices they possessed their own energy sources.
Irresistible - Sheppard's team visits a planet hoping to harvest its Stargate, but instead found a population governed by Lucius Lavin.
The Return, Part 1 - Dr. McKay reveals that the harvesting program has paid off when he unveils the "McKay-Carter intergalactic gate bridge."