"The Lamp Post was a DHARMA Initiative station located in a basement chamber beneath a church in Los Angeles, California in the United States. The station's purpose was to determine the Island's most probable location in space and time and identify windows of opportunity to travel there. It was the only known DHARMA station to exist off of the Island"
and another tid bit --
"The ledger contains information relating to the location and properties of the Island. It is the only description of the Island and how to get there that ever made it back to the outside world. This information was used by Alvar Hanso to locate the Island and to place DHARMA Initiative personnel there, and now Charles Widmore, who covets the Island for himself, intends to buy the ledger to use it for the same purpose"