Hurricane María was classified as a strong Category 4 hurricane on the Saffir-Simpson hurricane wind scale before making landfall in Yabucoa, Puerto Rico, U.S.A. on Sept. 20, 2017. The aftermath of hurricane María was a devastated island with at least 64 people killed, severe infrastructure loss, and numerous geotechnical failures related to the intense rainfall and strong winds associated to this extreme event. This report summarizes the event timeline and the geotechnical consequences of María’s path across Puerto Rico. The impacts of hurricane María on infrastructure and geomorphology are documented through the data and observations of the engineers and geologists that participated as members of the Geotechnical Extreme Events Reconnaissance (GEER) team. The reconnaissance mission took place between October 25 and November 6 of 2017. The GEER report summarizes observations on geotechnical impacts such as: the Guajataca Dam spillway failure; coastal erosion events, including foundation failures due to coastal erosion in Córcega, Rincón; bridge abutment scour failures; over 2,000 landslides along the PR highway system (e.g., along the PR-10, region of Lares, Barranquitas and Utuado); foundation failures; and other failures related to this destructive hurricane. Rainfall-induced landslides in Puerto Rico have been a serious recurring problem observed in the different physiographic regions of the island as result of María and other hurricanes such as Hortense (9/10/1996), Georges (9/21-22/1998), and Debby (8/22/1999). The pass of hurricane María triggered thousands of landslides. The most common type of failure mode consisted of shallow debris flows, but many deeper seated failures were also observed, typically at sites with a road fill and blocked drainage. The geotechnical failures presented in this report provide insight to help identify typical modes of failure and to help the engineering community adapt and improve design and construction practices to improve resiliency of our infrastructure and lifelines.