  We use neutron scattering to study the structural distortion and
antiferromagnetic (AFM) order in LaFeAsO$_{1-x}$F$_{x}$ as the system is doped
with fluorine (F) to induce superconductivity. In the undoped state, LaFeAsO
exhibits a structural distortion, changing the symmetry from tetragonal (space
group $P4/nmm$) to orthorhombic (space group $Cmma$) at 155 K, and then
followed by an AFM order at 137 K. Doping the system with F gradually decreases
the structural distortion temperature, but suppresses the long range AFM order
before the emergence of superconductivity. Therefore, while superconductivity
in these Fe oxypnictides can survive in either the tetragonal or the
orthorhombic crystal structure, it competes directly with static AFM order.
