Cook County property record for 503 S William St, Mount Prospect, IL 60056
| Property Type | Single Family Home |
|---|---|
| Details | 4 bd · 2.5 ba · 1,432 sqft · built 1956 |
| Lot Size | 0.166 acres (7,236 sqft) |
| Owner | Individual Name on File |
| Last Sale | $205,000 (Jun 1999) |
| Tax Bill | $8,547 (2023) |
| Deeds & Mortgages | Oct 2020 Transfer |
| Flood Zone | Zone X (minimal risk) |
| APN | 08-12-406-002 |
| Primary APN | 08-12-406-002 |
|---|---|
| Alternative APN |
|
| Bedrooms | 4 Beds |
|---|---|
| Full Baths | 2.5 Baths |
| Half Baths | 1 Half Bath |
| Total Rooms | 6 Rooms |
| Stories | 1 Story |
| Building Area | 1,432 sqft Living Area |
| 1st Floor Area | 1,432 sqft |
| Year Built | Built 1956 |
|---|---|
| Effective Year Built | Effective 1957 |
| Architectural Style | Bungalow |
| Exterior Material | Brick/Stone |
| Construction Type | Frame |
| Roof Material | Asphalt |
| Lot Area | 7,236 sqft (0.166 acres) |
| Garage Type | Attached |
| Parking Spaces | 1 Parking Space |
| Cooling System | Central |
|---|---|
| Heating System | HVAC |
| Street Address | 503 S WILLIAM ST |
|---|---|
| City | MOUNT PROSPECT |
| State | IL |
| Zip | 60056-3954 |
| Property Category | Residential |
| Property Type | Residential > Single Family > Home |
| Legal Description | (PLEASANT) HEIGHTS ADD TO (MOUNT)(PROSPECT) SUB OF LT S 3&4 IN OEHLERKINOIS DIVISION IN SE SEC 12-41-11 |
| Legal Range | 11E |
| Legal Township | 41N |
| Legal Section | 12 |
| Legal Subdivision | PLEASANT HEIGHTS ADD TO MOUNT PROSPECT |
| Legal Block | 3 |
| Legal Lot Number | 3,4,S |
| Jurisdiction | COOK IL |
| Township / Civil Division | ELK GROVE |
| Census Block Group | 3 |
| Census Block | 3011 |
| Census Tract | 804901 |
503 S William St is owned and occupied by an individual who acquired it in April 2020.
Source: Cook County records, as of May 27, 2026
Owner names and exact recorded amounts are on file and can be viewed instantly on this page with a free 10-day trial.
| Owner of Record | Individual Name on File |
|---|---|
| Mailing Address | 503 S WILLIAM ST, MOUNT PROSPECT, IL 60056-3954 |
| Occupancy | Owner Occupied |
| Owner Type | Individual |
| Deed Names | Name on Deed |
|---|---|
| Last Sale | Jun 16, 1999 · Amount on File |
| Deed Sale | Jun 16, 1999 · Amount on File |
| Deed Document Number | 1999775 |
| Last Transfer Date | Apr 1, 2020 |
| Transfer Doc | 0000041012 |
| Record Updated | Oct 29, 2026 |
| Document Type | Affidavit of Death |
|---|---|
| Jurisdiction | COOK IL |
| Recording Date | Oct 8, 2020 |
| Property Address | 503 S WILLIAM ST, MOUNT PROSPECT, IL 60056-3954 |
| Document Number | 2028241013 |
| Instrument Date | Apr 1, 2020 |
| Instrument | 28241013 |
| Transaction Type | Transfer |
| Record Updated | Oct 29, 2020 |
| Title Company | NOT AVAILABLE |
| Name | Verified Name |
|---|
| Name | Verified Name |
|---|---|
| Address | 503 S WILLIAM ST MOUNT PROSPECT IL 600563954, MOUNT PROSPECT, IL 60056-3954 |
Source: Cook County assessment roll, as of May 27, 2026
| Type | Name |
|---|---|
| State | Illinois |
| County | Cook County |
| County Subdivision | Elk Grove Township |
| Municipality | Mount Prospect Village |
| Secondary School District | Township High School District 214 (09 - 12) |
| Elementary School District | Mount Prospect School District 57 (PK - 08) |
| Year | Tax Bill | Assessed Value | Assessed Market Value |
|---|---|---|---|
| 2025 | $41,277 Land $8,683 Building $32,594 | $412,770 Land $86,830 Building $325,940 | |
| 2023 | $8,547.00 (+4.36%) | ||
| 2022 | $8,190.00 Homeowner's exemption | $34,000 Land $7,236 Building $26,764 | $340,000 Land $72,360 Building $267,640 |
Assessed value and assessed market value are set for property tax purposes, not market price estimates; both are a fraction of this property's market value.
FEMA maps place 503 S William St in Zone X, an area of minimal flood risk, though there have been 6 flood claims nearby since 1987.
Source: FEMA National Flood Hazard Layer, effective February 11, 2026 · OpenFEMA NFIP redacted claims and policies, as of September 2026
| FEMA Flood Zone | Zone X minimal risk |
|---|---|
| Flood Insurance Requirement | Not required lenders may require it |
| Community Rating System | Class 6 (20% premium discount) |
| Nearby Flood Policies | 2 in force |
| Nearby Flood Claims | 6 (1987–2007) |
| Claims Outside the SFHA | 2 of 6 |
| Most Recent Claim | Aug 2007 · Severe Storms And Flooding |
| Claims by Event |
|
Values are read at the parcel center point; flood claims are located to the census block group, not this parcel; lenders make the official flood determination.
The area around 503 S William St has no burnable land within ember reach, so its wildfire risk is not rated.
Source: USDA Forest Service Wildfire Risk to Communities (2nd edition), as of 2024
| Wildfire Risk | Not rated no burnable land within ember reach |
|---|
Values cover an area roughly 900 ft across, not the parcel itself; insurers use their own ratings.
Source: EPA Safe Drinking Water Information System, as of September 2026
| Water System | MOUNT PROSPECT serves 41,000 people · EPA ID IL0311980 |
|---|---|
| Water Source | Purchased surface water from NORTHWEST SUBURBAN MUNICIPAL JAWA |
| Last State Inspection | Aug 2025 |
| Lead | 2 ppb (2026–2028) action level 15 ppb |
| Water Quality | None last 10 years |
|---|---|
| Treatment and Procedure | None last 10 years |
| Monitoring and Reporting | 11 last 3 years |
Results are for the whole water system, not water tested at this address; lead at the tap also depends on the building's own pipes. The service area is an EPA estimate; the actual supplier may differ.
Source: FCC Broadband Data Collection, based on 671 locations within half a mile, as of December 31, 2025
| Provider | Max Down / Up (Mbps) |
|---|---|
| AT&T Fiber · DSL in parts of the area | 5,000 / 5,000 |
| Xfinity Cable | 2,000 / 250 |
| Astound Broadband Cable | 1,500 / 50 |
| Verizon Fixed Wireless | 1,000 / 75 |
May also be available: T-Mobile.
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