State and local agencies in Illinois publish solicitations through BidBuy, Illinois' procurement portal. To respond you'll generally need to register there as a vendor, select the commodity or service codes that describe what you sell, and watch the due dates — most state bids close within two to four weeks of posting, and late submissions are rejected outright.
Unlike federal contracting, state and local procurement rarely requires a SAM.gov registration or a UEI, and set-aside programs vary by state (many run their own small, minority-, women-, or veteran-owned business certifications). Purchasing thresholds also differ: smaller buys are often handled by informal quotes directly with the agency, while larger ones go through a formal sealed-bid or RFP process.
GovSeeker tracks the Illinois feed alongside SAM.gov, FPDS, grants, and two dozen other state portals, so you can search all of it from one place and get alerted when something matches your capability statement.