We completed a shoreline survey of Phragmites occurrence and adjacent land use along more than 8,400 km of shoreline in the Maryland and Virginia portions of the Chesapeake Bay and its tidal tributaries. Phragmites occurred along 14.6% of Maryland estuarine shoreline in the mid-to-upper portion of Chesapeake Bay, but along only 2.0% of the surveyed Virginia shoreline in the mid-to-lower portion. The dramatic difference in occurrence was not related exclusively to high salinity restrictions on plant distribution in the lower portion of the bay since most of the survey was completed in mesohaline to oligohaline sections of the estuary. Phragmites occurrence was highest—up to 30% of all shoreline—in the upper northeastern section of the bay and was over-represented adjacent to cleared but undeveloped land. Although Phragmites was found growing adjacent to all types of land uses including undisturbed forest in the mid-to-upper estuary, its occurrence was positively correlated with the percentage of agricultural shoreline. The extensive Phragmites occurrence throughout the upper estuary suggests that both local and regional environmental factors of management concern may contribute to the suspected spread of Phragmites along both Maryland and Virginia shoreline.