Before the outbreak, the campsite was a nature park area that had a dense forest, mountain cliffs which helped form a quarry, and a lake/river of water. Numerous animals such as squirrels, birds, deer, and fish all live in the area, feeding off of the vegetation. The State of Georgia most likely allowed campers and hikers to use this area as a public park space to hike, camp, fish, and rock-climb.
Prior to the outbreak, all refugees headed towards the city of Atlanta for safety and protection by the U.S. Military. However, infected individuals also made their way to the city and completely overran the shelter and outposts. When Shane Walsh and Lori Grimes see that the city is overrun and the subsequent destruction of the military installation, they decide to set up an outpost at the quarry just outside the city. Ed Peletier, his wife Carol, and their daughter Sophia also joined them and helped establish the campsite. Other survivors from the city and nearby area eventually see the survivors and join them at the campsite to establish a base of operations there.
They used the resources in the area to continue on their daily lives such as food, water, shelter, and safety from the infected. Andrea and her sister, Amy, fished on the lake, Merle and Daryl Dixon hunted, some of the women washed the clothes using the lake/river, and Dale Horvath mentions that the mountain cliffs provide protection since they are away from the city and loud sounds would be hard to pin-point in that location. However, the survivors occasionally have to make trips to the city for other supplies such as equipment, tools, and medicine.
The walkers (after running out of "food" in the city) began to make their way into more rural areas. A walker does wander into the camp and is seen eating part of a deer, later several walkers make their way into the campsite causing several casualties and several survivors were killed or bitten. Realizing that the walkers are making their way outside of the city and that this location was compromised, the remaining survivors decided to flee to the Center for Disease Control in Atlanta (with the exception of Morales and his family, who head to Birmingham, Alabama, to find their relatives).