Using new reconstructions of the Laurentide Ice Sheet and estimates of glacial-age precipitation suggested by a general circulation model, we calculated the freshwater fluxes derived from meltwater and precipitation runoff from North America to the North Atlantic and Arctic Oceans during the last deglaciation. Additional fluxes from iceberg-discharge events such as Heinrich events are not included, but would have supplemented fluxes calculated here. Meltwater plus precipitation runoff from each of 19 cryohydrological basins is routed to the oceans through one of five main injection sites: the Mississippi River to the Gulf of Mexico, the Hudson River to the North Atlantic, the St. Lawrence River to the North Atlantic, the Mackenzie and other Arctic rivers to the Arctic Ocean, and Hudson Strait to the Labrador Sea. We present new time series of freshwater fluxes to each of these injection sites for the last deglaciation. Our results indicate that large and rapid changes in freshwater flux to individual injection sites occurred as ice-margin fluctuations redirected runoff from one site to another. Although these abrupt rerouting events are not associated with a change in the total freshwater flux draining from the continent, they caused significant geographic changes in the flux entering the North Atlantic and Arctic Oceans during the last deglaciation which are of the same magnitude suggested by climate models to affect the rate of North Atlantic Deep Water formation, thus identifying routing events as a potentially important mechanism of abrupt climate change during the last deglaciation.