Light-level geolocators were deployed on 37 Red Knots at Monomoy National Wildlife Refuge, Cape Cod, Massachusetts, United States of America in Sep 2009 and eight were recovered at the same place a year later. Two of the eight geolocators failed halfway through the year, but the other six provided a full year's record of the birds' locations. All eight birds carried out the whole of their large-feather molt at Monomoy, after which they moved south to wintering areas, leaving between 29 Oct and 16 Nov. Four birds wintered on the U.S. Atlantic coast between Virginia and Florida, while four wintered in the Caribbean in areas not previously identified as important for Red Knots. During northward migration all six knots with geolocators still working stopped in the vicinity of the Nelson River estuary in the south-west corner of Hudson Bay, a site not previously identified as an important stopover for Red Knots. Migration speed (defined as the speed achieved between one stopover and the next, assuming the bird travelled along the great circle route) differed significantly between flights affected by headwinds (median 47 kph), those that took place in calm conditions (60 kph) and those affected by tailwinds (72 kph). We discuss the implications of our results for the conservation of the threatened rufa Red Knot population and highlight the need to investigate some of the sites the birds visited.