Escalating problems have prompted some parks, like Yosemite, to partially or fully close.
Although the trash cans are overflowing and the restrooms are without toilet paper, it's hoped this shutdown will pass without any casualties.
Grand Canyon National Park, for example, is open because after the last such federal shutdown the state of Arizona appropriated some revenues so that services such as shuttles and restrooms can remain open.
Many national parks remain open but with skeleton staffs. However, the number of visitors has swelled, "no one is at the gate", and "no one is collecting a fee".
Towns like these across the USA are financially dependent on businesses, from equipment rental services to, of course, locally-owned hotels and restaurants, most of which largely cater to national park visitors. Less civic-minded folks are illegally off-roading, tromping though delicate natural areas that are off-limits, and leaving behind mountains of garbage that can endanger wildlife.
According to the Washington Post, the Phillips Collection, the National Building Museum, President Lincoln's Cottage, and the Woodrow Wilson House are offering free admission to federal workers with government IDs-a move which significantly increased visitors numbers during shutdowns in the past.
Check out the photo of the garbage heap at the Washington Monument.
The shutdown has also forced the closure of campgrounds at Joshua Tree National Park in Southern California - where the dirty work is left to volunteers.
Staff shortages have created a sense of "lawlessness" in the parks, Brengel said.
At Sequoia and Kings Canyon National Parks in California, several areas have been closed because of lack of staff and unsanitary conditions. "A lot of these people are returnees and they're more than happy to give back to this park". Approximately 16,000 Park Service employees have been furloughed, and many attractions locally and nationally have been temporarily shuttered.
"Everyone loves the park".
Most visitors were being respectful of the desert wilderness and park facilities, Joshua Tree's superintendent David Smith said.
Specifically, they say vault toilets on the site are reaching capacity.
Laretig admits there are plenty of things he'd rather do than clean up the national park, but he says it's worth the effort.
In California, tourists have been relieving themselves on the side of the roads because Yosemite's restrooms and visitor centers have been shuttered since December 22 when the shutdown began, the Los Angeles Times reported.
Other parks were also seeing the effects of mounting garbage.
Yosemite National Park officials closed some minimally supervised campgrounds and public areas within the park that were overwhelmed on Monday.