PCT backpackers want to know what the rules are and where they apply. That requires knowing the land boundaries the PCT crosses and who manages that land.
Private Land
The PCT is only on private land for the first 20 miles north of the Columbia River (mm 2150.4 to mm 2153.4 and again from mm 2162 to 2170.4). After those first 20 miles, the PCT is on public land all the way to the Canadian border.
Public Land
I don't think the PCT is on any state land, except maybe State Route easements, so when we are talking about public land, we are talking about federal land.
At a high level, and in the context of the PCT in Washington, federal land is divided into National Forests and National Park Complexes. Within National Forests there are Wilderness Areas, and Ranger Districts. Within National Park Complexes there are also Wilderness Areas, Recreation Areas, and typically one National Park. These different designations have different land management strategies.
National Park Complexes are managed by the National Park Service (NPS) under the Department of the Interior.
National Forests are managed by the United States Forest Service (USFS) under the Department of Agriculture.
In Washington the PCT runs through three National Forests and one National Park Complex, and it tangents a second National Park Complex. The PCT also briefly enters a Reservation. Note that 0.9 miles of the PCT crosses the Yakima Reservation managed by the Bureau of Indian Affairs.
National Parks
Mount Rainier National Park Complex (MRNP)
Mount Rainier National Park is inside the Mount Rainier Wilderness Area. The PCT does not enter the National Park at any point, but it does weave in and out of Mount Rainier Wilderness Area in four short segments over a nine mile stretch.
The PCT is currently exempt from National Park Service rules in this area. In this area follow Okanogan-Wenatchee National Forest rules for the William O Douglass Wilderness.
The trail enters the MRW between mm 2316 near Craig Lake, and mm 2325 just south of Naches Peak.
North Cascades National Park Complex (NCNP)
The North Cascades National Park Complex includes the Lake Chelan National Recreation Area, the Ross Lake National Recreation Area, the Stephen Mather Wilderness, and the national park. In terms of land area, Stephen Mather Wilderness is almost synonymous with the NCNP Complex. Only 6% of the complex is not part of Stephen Mather Wilderness.
For hikers and backpackers, one set of rules and regulations applies to the entire complex.
The PCT is in the NCNP Complex for 17.2 miles (between mm 2573 and mm 2591). South-to-north you enter the complex from Glacier Peak Wilderness at mm 2573. After briefly entering the Lake Chelan National Recreation Area, 3.4 miles later you enter the National Park at mm 2576.7, north of Howard Lake. You exit it at mm 2591, when you are between the peaks of Rainy Benchmark (west) and Stiletto Peak (east) you exit the complex and enter the Okanogan-Wenatchee National Forest.
If you visit the town of Stehekin, you are still in the Lake Chelan NRA thus still in the North Cascades National Park Complex.
National Forests
Gifford Pinchot National Forest (GPNF)
GPNF is on the west side of the Cascade Crest from the Columbia River to the south edge of Mt Rainier NP.
Okanogan-Wenatchee National Forest (OWNF)
From north of Goat Rocks WA, to Suiattle Pass the PCT is constantly moving between two national forests as it follows the Cascade Crest. South of Bear Gap (mm 2332.2) its the OWNF and the GPNF. North of there its the OWNF and the MBSNF.
The PCT first enters the OWNF at mm 2280.5, between Old Snowy Mountain and Knifes Edge. From Suiattle Pass (mm 2555.2) to the North Cascades NP the PCT is in the OWNF, and after you leave the North Cascades NP you are in the OWNF all the way to the Canadian border.
Mount Baker-Snoqualmie National Forest (MBSNF)
Again, north of Bear Gap the PCT weaves back and fourth between the OWNF and MBSNF. At Suiattle Pass (mm 2555.2) the PCT leaves the MBSNF never to return again.
Wilderness Areas
Wilderness Areas are areas with special protections from impact by man. Unlike the rest of the National Forest, they are not managed as a commodity. Wilderness Areas are managed by the National Wilderness Perservation System (US Fish and Wildlife and Bureau of Land Management also have some involvement in the NWPS which I do not understand). Motorized vehicles are always prohibited in a Wilderness Area.
Wilderness Areas can be subdivided into Permit Areas. An example of this near the PCT is the Enchantments Permit Area inside the Alpine Lakes Wilderness Area. The PCT runs through only one Permit Area, and that is the Stephen Mather Wilderness in the North Cascades National Park Complex described above.
Wilderness Areas the PCT passes through
In order south to north, these are the National Forest Wilderness Areas the PCT passes through.
Within Gifford Pinchot NF there's the Indian Heaven Wilderness (1984), the Mt Adams WA, the Goat Rocks WA, and the William O Douglas WA (1984)
Within the Mt Baker-Snoqualmie NF there's the Norse Peak WA (1984),
Spaning both the MBSNF and the OWNNF are the Alpine Lakes WA (1976), Henry M Jackson WA (1984), and Glacier Peak WA.
Within the Okanogan-Wenatchee NF there's the Lake Chelan-Sawtooth WA (1984), and the Pasayten WA (1968).
American Indian Reservation
Reservations are managed by the Bureau of Indian Affairs which is a branch of the Department of the Interior. The Yakama Indian Reservation was established by treaty in 1855. Note that Yakima is a mispelling of the correct tribal name Yakama.
0.9 miles of the PCT is in the Yakama Indian Reservation. That portion is in the Goat Rocks WA, south of Cispus Pass (mm 2275), on an east facing slope.
The original Cascade Crest Trail route did not enter the reservation and that trail still exists as a slightly longer alternate route on the opposite west facing slope.
EC Manning Provincial Park
If you legally enter Canada on the PCT (with a permit), you will be in EC Manning Provincial Park all the way to Manning Park Resort and Highway 3.