Many visitors on the holiday weekend were frustrated by the amount of trash they found.
"If you're at home you wouldn't leave your house like that, so that should apply here too," said Anna Gurski.
One reason for all of the refuse is the sheer number of visitors who hike the trails, set up picnics or play in the water. Each year more than three and a half million people visit the park.
"It's incredibly important to let people know that what they're leaving in this place may end up in part of their drinking water," said Daniel Rossman, whose Wilderness Society is pushing Congress to designate the Angeles National Forest as a national recreation area.
One simple solution Rossman suggested was to restart a program instructing visitors to carry out whatever they carry in to the park - especially trash.
However, funding for such a basic campaign is just not available at this time, proving that keeping our parklands clean is no walk in the park these days.