Cook County Property Parcel Sales 1999 to Present

Parcel sales for real property in Cook County, Illinois, from 1999 onward. The Cook County Assessor's Office uses this data to model fair market values for unsold properties. Sales are updated monthly but reported on a lag, with records populating months after their official recording date.

Use Cases

• Model property fair market value using historical parcel sale prices and recording dates.
• Analyze temporal trends in real estate sales activity across Cook County from 1999 to present.
• Link sale document numbers to the Cook County Clerk's records for detailed transaction research.
• Study the impact of property class code changes over time on assessed values.

Strengths

• Provides a multi-decade time series of property sales data starting from 1999.
• Monthly updates ensure ongoing data collection, though with a reporting lag.
• Includes documentation on property class codes and assessment levels for context.

Limitations

• Excludes non-arms-length transactions such as sales under $10,000, quit claims, and executor deeds.
• Data freshness is impacted by a reporting lag, with many records not appearing until months after the official recording date.
• Property class codes and their assessment details can change over time, complicating longitudinal analysis.

Provenance

Source

Cook County Assessor's Office, Cook County of Illinois.

Collection Method

Collected from recorded property sales, prepared according to the Assessor's Standard Operating Procedures for Open Data.

Time Range

1999 to present.

Freshness

Updated monthly, with data current as of the platform's last update in March 2026.

Geography

Cook County, Illinois, USA.