Wildfires often burn across boundaries affecting multiple jurisdictions, landowners and levels of government. Wildfire co-management across jurisdictions is expected to increase in complexity as wildfire severity, size, and frequency increase due to climate change, and growing populations bring more people into close proximity with wildfire. A systematic method to assess jurisdictional complexity for wildfire management is needed to effectively allocate resources and plan for future wildfire management conditions. Here, we developed an open-source framework of decision rules to count jurisdictions and landowners by coupling nearly 9,000 historic wildfire footprints that occurred across 43 U.S. states between 1999 and 2020 with geospatial jurisdictional data. We found that the number of annual wildfires greater than 500 acres has increased through time, with a proportional increase in the number of the highly complex (>7 jurisdictions; >3 levels of government) wildfires. Most wildfires burned 2–3 jurisdictions and 1 or 2 land ownerships, and the most common co-managed wildfires occurred on federal and private lands. On average, the western United States, specifically the Mediterranean California ecoregion, has more jurisdictionally complex wildfires, but the eastern United States, namely the Appalachian Mountains, has localized areas that experienced multiple wildfires with high and varied jurisdictional complexity. The prairies of Texas contained the largest extent of average low complexity wildfires. Of the 43 states that contained a wildfire, 41 had a census place that was burned or within 5 miles of a wildfire boundary, and overall, the annual number of census places near wildfires appears to be increasing through time. We demonstrate a framework that can be used to quantify jurisdictional complexity from observed wildfire boundaries and provide a baseline for discussing jurisdictional complexity at a national, regional, and sub-regional scale. This framework may also be adapted to other hazards or multi-jurisdictional phenomena that have geospatial boundary objects.