The Independent Inspector General submits a Quarterly Report to the President and the County Board. The Quarterly Report is released the 15th day of January, April, July, and October of each year. Quarterly Reports chronicle the number and type of investigations initiated, concluded or pending since the date of the last report. The Quarterly Report identifies the number and type of investigations (corruption, fraud, waste, mismanagement, unlawful political discrimination or misconduct) of any County employee, appointed officials, elected officials, contractors, subcontractors, persons seeking County Contracts, or persons seeking certification of eligibility for County contracts or other County Programs. The Quarterly Report identifies the number and type of investigations conducted by the OIIG regarding employees under the separately elected officials. The Quarterly Report identifies the number and type of recommendations made to any department heads or elected officials and whether or not the recommendation was followed.

Annual salaries paid to employees by the Cook County Comptroller as of March 5, 2013. Does not include deduction for furlough or closure days for employees subject to furloughs and closures. Does not include amounts paid by other governmental entities. For 2014 salaries see https://datacatalog.cookcountyil.gov/resource/hdna-35se

Archive of budget PDFs starting with fiscal year 2002.

This dataset provides the list of vendors and contracts to be executed by the Office of the Chief Procurement Officer and is updated 3 days before award.

M/W/DBE Participation Types
MBE = Minority Business Enterprise
WBE = Women Business Enterprise
DBE = Disadvantaged Business Enterprise
Native American (4)
African American (5)
Female (7)
Asian (8)
Hispanic (9)

This is the data set of residential sales used by the Cook County Assessor in their Computer Assisted Mass Appraisal system used to assess residential property values. This data set contains property information for every arm's-length residential sale in Cook County where class is within a specified list of classes. For disclaimers, see data set narrative at https://datacatalog.cookcountyil.gov/stories/s/p2kt-hk36

This data set was replaced by the more comprehensive data set Cook County Assessor's Sales.

Foreclosures recorded from January 1, 2012 through November 29, 2012

Employee payroll data for all Cook County employees excluding Forest Preserves, indicating amount of base salary paid to an employee during the County fiscal quarter. Salaries are paid to employees on a bi-weekly basis.
Any pay period that extended between quarters will be reported to the quarter of the Pay Period End Date. (e.g. If a Pay Period runs 02/21-03/05, that pay period would be reported in the Q2 period, as the end of the pay period falls in March - Q2)

The county fiscal quarters are:
Q1: December - February
Q2: March - May
Q3: June - August
Q4: September - November

The Employee Unique Identifier field is a unique number assigned to each employee for the purpose of this data set, that is not their internal employee ID number, and allows an employee to be identified in the data set over time, in case of a name change or other change. This number will be consistent within the data set, but we reserve the right to regenerate this number over time across the data set.

KNOWN ISSUE: Several records are missing Bureau and Office information. We are working on correcting this and will update the dataset when this issue has been resolved.

For data prior to Fiscal Year 2016, see datasets at https://datacatalog.cookcountyil.gov/browse?tags=payroll

A Note from the State's Attorney's Office as of 12/30/2024:

The Cook County State's Attorney's Office believes data transparency is an important accountability and public safety tool and is committed to providing Cook County residents with this critical information. Currently, we are working to make sure that the data we share is valid, accurate, and presented in a format that is useful to the public. Our goal is to have resumed updating the Cook County open data site within the first 100 days of the new administration.

Dataset Description:

The Initiation results data presented here reflects all of the arrests that came through the door of the State's Attorneys Office (SAO). An initiation is how an arrest turns into a “case” in the courts. Most cases are initiated through a process known as felony review, in which SAO attorneys make a decision whether or not to prosecute. Cases may also be indicted by a grand jury or, in narcotics cases, filed directly by law enforcement (labeled "BOND SET (Narcotics)" in this data). Included in this data set are the defendant counts by initiation and year. This data includes felony cases handled by the Criminal, Narcotics, and Special Prosecution Bureaus. It does not include information about cases processed through the Juvenile Justice and Civil Actions Bureaus.
Please use this link for more instructions and data glossary:
https://www.cookcountystatesattorney.org/resources/how-read-data

Single and multi-family (less than 7 units) property characteristics collected and maintained by the Assessor's Office for all of Cook County, from 1999 to present. The office uses this data primarily for valuation and reporting.

When working with Parcel Index Numbers (PINs) make sure to zero-pad them to 14 digits. Some datasets may lose leading zeros for PINs when downloaded.

Current property class codes, their levels of assessment, and descriptions can be found on the Assessor's website. Note that class codes details can change across time.

This data is improvement-level - 'improvements' are individual buildings on a parcel. Each row in a given year corresponds to a building e.g. two rows for the same parcel in one year means a parcel has more than one building.

Data will be updated bi-weekly. Rowcount and characteristics for the current year are only final once the Assessor has certified the assessment roll for all townships.

Depending on the time of year, some third-party and internal data will be missing for the most recent year. Assessments mailed this year represent values from last year, so this isn't an issue. By the time the Data Department models values for this year, those data will have populated.

NOTE: The Assessor's Office has recently changed the way Home Improvement Exemptions (HIEs) are tracked in its data. HIEs "freeze" a property's characteristics for a period of time with the intention of encouraging owners to improve their property without fear of assessment increases.

Historically, the updated, "improved" characteristics were saved in a separate file. However, in more recent years, the improved characteristics are saved in the main characteristics file. As such, the records in this data set from before 2021 do NOT include HIE characteristic updates, while those after and including 2021 DO include those updates.

For more information on HIEs, see the Assessor's Data Department wiki.

For more information on how this data is used to estimate property values, see the Assessor's residential modeling code on GitHub.

Township codes can be found in the legend of this map.

For more information on the sourcing of attached data and the preparation of this dataset, see the Assessor's Standard Operating Procedures for Open Data on GitHub.