The environmental conditions associated with changing the hydration state of active pharmaceutical ingredients (API) are crucial to understanding their stability, bioperformance, and manufacturability. Identifying the dehydration event using < 1 mu g of material is an increasingly important challenge. Atomic Force Microscopy indentation mapping is implemented at controlled temperatures between 25 and 100 degrees C, for nanoscale volumes of hydrated APIs exhibiting distinct dehydration behavior and anhydrous APIs as controls. For caffeine hydrate and azithromycin dihydrate, the relative mechanical modulus increases similar to 10-fold at dehydration temperatures. These are confirmed by conventional macroscopic measurements including Variable Temperature Powder X-ray Diffraction, Thermogravimetric Analysis, and Differential Scanning Calorimetry. Conversely, no such mechanical transition is observed for anhydrous ibuprofen or a proprietary anhydrous compound. AFM-based mechanical mapping is therefore demonstrated for small-volume determination of temperature-induced solid-state dehydration events, which may enable spatial or temporal mapping for future studies of dehydration mechanisms and kinetics as a function of commercially relevant nanoscale heterogeneities. (C) 2019 Elsevier B.V. All rights reserved.