Why Finding Property Lines Matters
Every property owner in Illinois eventually needs to know exactly where their land ends and their neighbor's begins. Whether you are planning a fence, adding a driveway, resolving a dispute, or simply satisfying curiosity, you need accurate information. The challenge is that some methods of finding property lines are reliable and some are not, and using the wrong one can lead to expensive mistakes.
The Most Reliable Method: Hire a Licensed Surveyor
The only method that produces a legally certified boundary location is a survey performed by a licensed Illinois Professional Land Surveyor (PLS). A PLS is licensed by the Illinois Department of Financial and Professional Regulation (IDFPR) under the Illinois Professional Land Surveyor Act (225 ILCS 330/). No other professional, and no online map or app, can provide a legally binding determination of where your property line sits.
When a surveyor visits your property, they research recorded plats, deeds, and historical survey data, then locate or set physical corner monuments on the ground. The resulting survey drawing and corner markers are what you need if you ever have to defend a boundary in court, apply for a building permit, or resolve a dispute with a neighbor.
Surveying costs in Illinois typically run:
- Downstate platted lot: $400 to $900
- Chicago metro area: $600 to $1,500
- Rural or acreage parcels: $800 to $2,500 or more depending on size and record availability
Public Records Methods
Before spending money on a survey, it is worth checking public records to understand what is already documented about your property. These methods will not give you a legally certified boundary, but they provide useful context and can reduce a surveyor's research time.
County Recorder's Office
Recorded plats, deeds, and prior surveys for your property are on file at your county recorder's office. Many Illinois counties have online portals where you can search by address or parcel identification number (PIN). The plat of subdivision for your neighborhood, if your property is in a platted subdivision, shows how the block was originally divided and includes dimensions for each lot.
Plat maps give you the intended dimensions of your lot as recorded, but they are not a substitute for a physical survey. Over decades, corners can be displaced or lost, and recorded dimensions do not always match what is found in the field.
Illinois GIS Atlas
The Illinois GIS Atlas at atlas.illinois.gov provides access to geographic data across the state, including links to county GIS and parcel viewer tools. From here you can navigate to your county's parcel data, see approximate lot boundaries overlaid on aerial imagery, and find your PIN. This is a helpful starting point for understanding your property's general shape and location relative to surrounding parcels.
County GIS Parcel Viewers
Most Illinois counties maintain their own GIS parcel viewer. These tools typically show parcel boundaries, ownership information, dimensions, and sometimes links to recorded documents. Cook County's Assessor GIS at cookcountyassessor.com is one of the more detailed county-level tools in the state. Downstate counties vary widely in the quality and currency of their online parcel data.
Important limitation: county GIS maps are not surveyed data. They are drawn from deed descriptions and recorded plats and can be off by several feet. Do not use them to place a fence or make any decision that depends on exact boundary locations.
Illinois State Geological Survey
The Illinois State Geological Survey (isgs.illinois.edu) maintains historical records that can be useful for older rural parcels where original survey data from the Public Land Survey System (PLSS) is relevant. The PLSS grid of townships, ranges, and sections underlies land descriptions across most of Illinois. For rural parcels with metes and bounds descriptions tied to PLSS quarter sections, ISGS data can help a surveyor understand the historical record.
Physical Corner Markers
Illinois surveyors set physical monuments at property corners when they complete a survey. These are typically iron pins, rebar, or iron pipes driven into the ground, sometimes with a cap identifying the surveyor or survey firm. Finding these markers is often the most direct way to identify a corner location without hiring a new surveyor.
To search for corner markers:
- Use a metal detector along the expected property line, especially at corners where lines change direction
- Check slightly below grade, as frost heave and settling can bury pins over time
- Look at the edges of concrete or asphalt features, as markers are sometimes set flush with pavement
- Review your recorded plat or prior survey drawing for notes about monument type and location
If you find markers, do not assume they are still in the correct position. Markers can be disturbed by construction, grading, or landscaping. If you need to rely on a corner location for a fence or structure, have a licensed surveyor verify that the marker is still in the correct position.
What Not to Rely On
Several sources that seem helpful are not accurate enough for boundary decisions:
Smartphone GPS Apps
Consumer GPS apps and mapping tools like Google Maps or Apple Maps have positional accuracy in the range of five to fifteen feet under good conditions. Property lines in dense urban or suburban areas can be only a few feet wide. These apps are not useful for locating a boundary precisely.
Your Neighbor's Word
A neighbor's belief about where the line sits is not a legal determination of the boundary. Even longtime neighbors who have lived there for decades may have wrong assumptions, passed down from prior owners. A line that “everyone knows” is rarely as certain as people believe.
Existing Fences
An existing fence in a neighborhood is often assumed to mark the property line. In reality, many older fences were installed without a survey and may be off by a foot or more. Do not place a new fence based on the assumption that an existing fence is on the line.
When You Need a Full Survey
For many purposes, reviewing public records and checking for existing corner markers is enough to get oriented. But if any of the following apply, a licensed survey is the right step:
- You are planning to build a fence, shed, deck, or addition near the property line
- You are in a boundary dispute with a neighbor
- You are buying or selling a property with unclear deed descriptions
- Your lender or title company has requested a survey
- You want to verify that an existing structure is entirely within your property
- You are applying for a building permit that requires boundary information
How to Hire a Licensed Illinois Surveyor
Illinois Professional Land Surveyors are licensed through IDFPR. To verify that a surveyor holds a current license, use the license lookup tool at idfpr.illinois.gov. When getting quotes:
- Have your property address and PIN ready
- Know the approximate lot size and whether the property is in a recorded subdivision
- Ask what the deliverables include, specifically whether you get a certified drawing and physical corner monuments set or located
- Get at least two quotes before committing
Ready to find a licensed Illinois land surveyor? Search the Illinois land surveyor directory to find professionals in your county and get quotes for your project.