Engineering firms in Chicago: 1,434 offices, Illinois's separate structural license and how to check a design firm

This report is for developers, owners, architects and agencies hiring a Chicago-area engineering firm, engineers choosing where to work, and B2B sellers whose customers are design firms. It has the Census count by county, the state's own registration numbers, the Illinois structural rule that shapes who can do what, how to vet a firm and a prospecting example built on that rule.

The Census count

County Business Patterns 2023 reports NAICS 541330 (Engineering Services) for the Chicago-Naperville-Elgin, IL-IN Metro Area (CBSA 16980):

In bands: 1,132 offices with 1 to 19 employees, 256 with 20 to 99 and 46 with 100 or more. The last figure is the total less the smaller bands, because the Census Bureau doesn't publish the two largest cells; it implies three offices with 500 or more employees. More than half the offices (51.4%) have fewer than five people.

The count is of establishments with paid employees, so a firm with Loop and suburban offices counts twice, and engineers working alone aren't counted. Engineers on the payroll of manufacturers, utilities or contractors are counted in those industries.

Where the offices are

Average pay is our calculation from CBP payroll, for the six largest counties. Cook has 43.5% of the metro's offices and 54.0% of its jobs. DuPage, with 294 offices, is the second hub, and its offices are mid-sized: 51 have 20 to 49 employees, almost as many as Cook's 66. The Census Bureau marks Lake County, Illinois's employment as moderately affected by its confidentiality noise. The two Indiana counties fall under Indiana's engineering board, not Illinois's.

What the state's registry adds

The Illinois Department of Financial and Professional Regulation (IDFPR) registers both engineers and the firms that offer their services. Its Active License Report for 1 October 2026 counts, statewide:

The last row is our sum of every design firm category that includes professional or structural engineering; 819 of those firms include structural engineering. Registrations include out-of-state firms licensed to work in Illinois, so they don't map one-to-one onto the Census count of local offices.

The structural rule

Illinois regulates structural engineering under its own act. IDFPR's guidance is blunt: "A Professional Engineer in Illinois cannot offer or perform any Structural services. Only an Illinois licensed Structural Engineer can perform Structural services in Illinois." The structural act has none of the industrial, railroad or manufacturing exemptions in the professional engineering act. IDFPR lists the work it covers as including the design or analysis of bridges, columns, girders, foundations, wind and seismic load calculations, retaining walls of any height, structural forensics and "structures of any kind," permanent or temporary.

Professional engineering, by contrast, isn't discipline-specific in Illinois: a licensed PE may practice any branch they're competent in (civil, mechanical, electrical, environmental, geotechnical, fire protection and so on), except structural. Since April 2024, Illinois no longer accepts the NCEES Civil/Structural PE exam toward a PE license.

How to check a Chicago engineering firm

1. Confirm the firm's design firm registration in IDFPR's license lookup, and check which professions it's registered for.
2. For anything structural, ask for the SE license of the engineer who will seal the drawings, and look it up too. A firm registered only for professional engineering will need a structural subconsultant.
3. Ask for comparable local projects with the permitting jurisdiction (City of Chicago, a suburb or IDOT) and how review went.
4. Compare scope and exclusions, including construction administration, before fees.
5. For Indiana sites in Lake or Porter County, check the Indiana license instead.

Selling to Chicago engineering firms

Illustrative example. The company, rates and results are fictional, to show the method.

Prairie Structural (prairiestructural.example) is an SE-licensed firm that does structural work as a subconsultant. The Illinois rule hands it a defined market: design firms that can't do structural work themselves.

• Illinois design firms registered for professional engineering but not structural: 1,359 (PE only) + 120 (architecture and PE) + 155 (surveying and PE) + 4 (surveying, architecture and PE) = 1,638.
• Architecture-only design firms, which also need structural engineers: 1,456.
• It assumes 60% of the PE firms work in the Chicago metro and a quarter of those regularly need structural input on equipment supports, rooftop units or small additions: about 245 firms.
• Winning 20 as repeat clients at $40,000 of structural fees a year each is $800,000.

Its first contacts are the principals and project managers at MEP and civil firms, who meet the rule every time a rooftop unit needs a new support. Sorting 1,638 registrations into Chicago-area MEP and civil practices, and finding who manages projects there, is the research Bebop does for each account.

Subject: Structural on your rooftop and equipment jobs

Hi [first name],

In Illinois, the support frames, dunnage and roof openings on an MEP job need structural design sealed by an SE, and that's often where the schedule slips.

We're an SE-licensed firm that only works as a subconsultant to engineers. We turn equipment support and framing calcs in five working days, sealed for City of Chicago and suburban permits. Could we price your next one?

[Your name], Prairie Structural

Next step: for the national firms that run large Chicago offices, see the largest engineering firms.