Food access across Illinois

The active bundle combines USDA SNAP retailers, Illinois WIC vendors, Census urban areas, USDA 2025 SNAP-authorized Retailer Access Map, 2024 ACS estimates, CDC PLACES, OpenStreetMap opening-hours tags, and GraphHopper fixed-distance isochrones generated on a local Windows computer.

Qualifying grocery views exclude convenience stores, dollar stores, pharmacies, farmers markets, and specialty stores unless an administrator reviews and reclassifies a vendor. Any WIC vendor intentionally includes WIC-authorized pharmacies and other non-grocery vendors.

Population-access figures test routed coverage at the internal point of every populated 2020 Census block, then weight each block by its decennial population to get the covered share of a block group. Census blocks are the smallest geography the Bureau publishes population for, so residents are counted where they actually live rather than spread evenly across a block group. That covered share is applied to the block group's current ACS population. Where no populated block resolves inside a block group the estimate falls back to an evenly spaced point grid, and the block group records which method was used. Population uniquely served estimates residents for whom one store is the only routed provider in the selected view. The vehicle adjustment uses the block-group no-vehicle household rate as a planning proxy and does not identify individual households. ACS population, poverty, and vehicle access are all block-group measures, from tables B01003, C17002, and B25044. CDC health measures and USDA low-income / low-access designations remain tract-level because those source datasets are not published at block-group resolution.

Food access priority index: Each selected lens and travel mode receives a 0-100 planning score: 40% statewide percentile of estimated residents outside routed access, 25% percent of the block group outside routed access, 20% statewide percentile of block-group poverty, and 15% statewide percentile of block-group no-vehicle households. The score is weighted toward the number of residents affected rather than the share of land area affected, because a small block group can fall entirely outside a coverage area while holding few people. Where the ACS suppresses a block-group value the tract measure is substituted, and the affected block group records which resolution was used. Routed coverage is weighted using populated Census blocks; a sampled point grid is used only when no populated block can be resolved for a block group.

Address and ZIP assessments use the full indexed routed geometry in the active bundle. ZIP and city searches are local. Street-address searches use the U.S. Census TIGER address-range geocoder only to estimate a location; it does not confirm USPS deliverability. No external routing API is used.