{
  "name": "Great River Road, Alton to Grafton",
  "slug": "great-river-road-il-100-alton-grafton",
  "url": "https://www.bestdrivingroads.com/roads/great-river-road-il-100-alton-grafton/",
  "summary": "The Alton to Grafton stretch of the Great River Road, 15 miles of four-lane highway between the Mississippi and wooded limestone bluffs, past the Piasa Bird mural and the stone village of Elsah to the Illinois River confluence.",
  "roadNumbers": [
    "IL 100"
  ],
  "location": {
    "country": "United States",
    "region": "Illinois",
    "start": {
      "name": "Alton",
      "lat": 38.890253,
      "lon": -90.186611
    },
    "end": {
      "name": "Grafton",
      "lat": 38.969789,
      "lon": -90.435208
    }
  },
  "measurements": {
    "lengthMiles": 15.1,
    "lengthKm": 24.3,
    "driveMinutes": 28,
    "corners": 10,
    "hairpins": 0,
    "maxGradientPercent": 3,
    "summitMetres": 140.3,
    "elevationConfidence": "measured",
    "difficulty": "easy",
    "tightnessOutOf10": 3
  },
  "timing": {
    "bestSeasons": [
      "spring",
      "summer",
      "autumn",
      "winter"
    ]
  },
  "conditions": {},
  "hazards": [
    "Closed by major river floods, as in May 2017",
    "Heaviest traffic on autumn weekends",
    "Lots of motorcycles on fine weekends"
  ],
  "scenery": [
    "valley",
    "forest"
  ],
  "pointsOfInterest": [
    "Piasa Bird",
    "Mississippi River Overlook",
    "Elsah Historic District",
    "Grafton"
  ],
  "geometry": {
    "pointCount": 71
  },
  "attribution": {
    "source": "bestdrivingroads.com",
    "citation": "Cite with a link to the road page. Stats are measured from the mapped line; where elevationConfidence is \"approximate\" the 30 m DEM cannot resolve that line and the elevation figures are indicative.",
    "roadGeometry": "(c) OpenStreetMap contributors, ODbL",
    "terms": "Facts are free to cite with attribution; bulk reproduction of the catalogue requires permission (simon@keane.studio)."
  },
  "updated": "2026-10-11"
}