The Illinois Fence Act is not a universal backyard rule
The Illinois Fence Act, 765 ILCS 130, provides a partition-fence framework when both adjoining tracts are used for farming or grazing. It includes fence-viewer procedures and contribution rules. A homeowner in a platted subdivision should not cite that law as automatic authority to charge a neighbor for a privacy fence.
If agricultural land is involved, read the Act and ask the township or an Illinois attorney how it applies before construction. A surveyor can determine and mark the boundary; the surveyor does not decide a neighbor's payment obligation.
Residential projects turn on local rules
Illinois municipalities set their own standards. The Village of Westmont's current fence guide, for example, requires a permit application and a legal plat of survey. That is a Westmont requirement, not a statewide rule. Ask the exact jurisdiction what it needs and whether it will accept an existing plat or requires new work.
Use the old plat carefully
An older closing file may contain a plat of survey. Check its date and compare the drawing with later fences, garages, additions, drives, patios, and sheds. Send it to the original surveyor when possible. Do not scale a post location from a reduced copy or assume a curb, utility box, tax map, or neighboring fence is a boundary monument.
Mark the boundary when the placement carries risk
The Illinois Professional Land Surveyor Act defines establishing, reestablishing, locating, and monumenting real-property boundaries as professional land surveying. That work is appropriate when corners are missing, the old fence conflicts with records, the route is irregular or wooded, a neighbor objects, or the local reviewer needs dimensions tied to established lines.
Specify the field result
Tell the surveyor whether the contractor needs all corners, one fence-side line, stakes at intervals, or a signed plat. Ask what will be set in the field and what document will be delivered. Then show the markings to the contractor, document them, and request utility marking before excavation.