  We present a new set of leading twist parton distribution functions, referred
to as "CJ15", which take advantage of developments in the theoretical treatment
of nuclear corrections as well as new data. The analysis includes for the first
time data on the free neutron structure function from Jefferson Lab, and new
high-precision charged lepton and W-boson asymmetry data from Fermilab. These
significantly reduce the uncertainty on the d/u ratio at large values of x and
provide new insights into the partonic structure of bound nucleons.
