The ASEH invites proposals for its 2013 conference that will convene 3-6 April in Toronto, Canada - North America’s fifth largest city and one of the fastest growing and most ethnically and linguistically diverse places on the continent. Toronto’s location, amid lakes and rivers, has long made it a site of confluences and crossings. An important aboriginal fishing site, a key portage during the fur trade, and now a “global city,” Toronto has at different moments been a nodal point for flows of fish, furs, peoples, and capital. Environmental history challenges many familiar boundaries. Our theme, “Confluences, Crossings, and Power” calls attention to flows and boundary-crossings, while also highlighting the role of power in shaping movements and their direction. We seek panel and roundtable proposals that engage with this theme in many different guises: political borders and the flows across them; the interactions of water and land; the crossings of peoples, species, and cultures; movements of pollutants across landscapes and bodies; resource and commodity flows; urban-hinterland relationships; the flows and frictions that constitute "globalization”; the crossing of intellectual boundaries; and the emergence of transdisciplinary collaborations.We also see the conference’s location in Toronto as an opportunity to encourage non-US topics, transnational and comparative perspectives, and presentations focused on the Great Lakes and high-latitude regions.