By state statute, the county is custodian of PLSS corners. A common activity by counties is the marking of corners with sturdy, modern monuments, a process called remonumentation. In a number of counties, this work has been completed.

PLSS corner monuments and associated witness posts.

In determining the correct location of a PLSS corner, a land surveyor considers a variety of records and field evidence. The goal is to identify an unambiguous location and then install a labeled monument in the ground at the spot. Often a highly visible witness post is also installed nearby and further documented by a distance and direction from the PLSS corner. The surveyor may also prepare a "tie sheet", a map of the area surrounding the corner showing distances and directions to nearby objects. The tie sheet helps others find the corner and documents the corner's location in case it is disturbed or destroyed.

The corner monument and/or witness post typically will be labeled with the town, range, and specific corner's identity. Where a corner is surrounded by pavement, it may be marked with a metal cap flush with or below the surface.  

See this video of land surveying and what a monument looks like in Vernon County, Wisconsin:

In the absence of an officially sanctioned monument, a land surveyor may set a stake in the ground at a point to be used as the PLSS corner. In some cases, more than one such stake may be left in the presumed location of the corner, leading to confusion.

During the 1930's, Civilian Conservation Corps crews did some remonumentation in forested areas; the documentation of their work, and its quality, is not clear.

Horizontal coordinates; elevations

Sometimes horizontal coordinates are measured for a monumented PLSS corner. Having such information available facilitates the surveying and mapping of land parcels. The accuracy of horizontal coordinates depends on the methods used to develop the values.

Sometimes PLSS corner monuments simultaneously serve as points in a geodetic control network. A good example of this approach is the counties served by the Southeastern Wisconsin Regional Planning Commission, where both horizontal and vertical control values are routinely acquired for PLSS corner monuments.

Progress toward remonumentation

The State of Wisconsin established a statutory mandate in 1970 calling for counties to complete remonumentation within 20 years, but provided no funds for this work. The progress toward complete remonumentation has varied greatly across the state. To determine the status of a specific section corner monument, it may be necessary to contact the county (County Surveyor if such a position exists or the Land Information Office).

Changes around water bodies

Where reservoirs were filled with water after the original PLSS corners were set, some corners became submerged. Nevertheless, at least some of these are indicated on maps. Along the shorelines of some large lakes (e.g, the Great Lakes) and in some flood plains, there have been some PLSS corners lost to major erosion as the forces of nature modify the landscape.

Corners in roadways

Many PLSS corners are today in roadways, since it was more practical to acquire public right of way for local road construction along property boundary lines. Some of these corners are covered by pavement or may be flush with the surface.

Geographic reference system

While the PLSS was developed to mark and convey property, it has also been used in a more general sense to describe land and events on the land. For instance, a large volume of records has been collected over the years where the geographic reference is of the type "SE 1/4 of Section 9, T4N R7E." Examples are rare plants, wildlife, and wells drilled. The location might be further refined to "NW 1/4 of the NE 1/4 of the SE 1/4" which reduces the area to approximately 10 acres. Note that the phenomenon observed may best be characterized by a point rather than an area, yet the geographic reference is to an area.

Sometimes information that carries a very precise location will be deliberately modified when provided to some users. For instance, a rare plant may have been found growing and its position recorded by GPS to an accuracy of a few meters. Nevertheless, when knowledge of the plant's existence is provided to some users, it may be reported only to PLSS section. This deliberate vagueness provides protection against disturbance of the plant.

Ocasionally a psuedo-PLSS "grid" will be extended over water or non-PLSS lands to provide a reference system for field data collection and resource management. One example is the project to harvest highly valuable logs lost from timber barges in the late 19th century in Chequamegon Bay in Lake Superior.