Tungsten nitride layers, 1.45-μm-thick, were deposited by reactive magnetron sputtering on MgO(001), MgO(111), and Al2O3(0001) in 20mTorr N2 at 700°C. X-ray diffraction ω-2θ scans, ω-rocking curves, φ scans, and reciprocal space maps show that all layers exhibit a cubic rock salt structure, independent of their N-to-W ratio which ranges from x=0.83–0.93, as determined by energy dispersive and photoelectron spectroscopies. Growth on MgO(001) leads to an epitaxial WN(001) layer which contains a small fraction of misoriented grains, WN(111)/MgO(111) is an orientation- and phase-pure single-crystal, and WN/Al2O3(0001) exhibits a 111-preferred orientation containing misoriented cubic WN grains as well as N-deficient BCC W. Layers on MgO(001) and MgO(111) with x=0.92 and 0.83 have relaxed lattice constants of 4.214±0.005 and 4.201±0.031Å, respectively, indicating a decreasing lattice constant with an increasing N-vacancy concentration. Nanoindentation provides hardness values of 9.8±2.2, 12.5±1.0, and 10.3±0.4GPa, and elastic moduli of 240±40, 257±13, and 242±10GPa for layers grown on MgO(001), MgO(111), and Al2O3(0001), respectively. Brillouin spectroscopy measurements yield shear moduli of 120±2GPa, 114±2GPa and 108±2GPa for WN on MgO(001), MgO(111) and Al2O3(0001), respectively, suggesting a WN elastic anisotropy factor of 1.6±0.3, consistent with the indentation results. The combined analysis of the epitaxial WN(001) and WN(111) layers indicate Hill's elastic and shear moduli for cubic WN of 251±17 and 99±8GPa, respectively. The resistivity of WN(111)/MgO(111) is 1.9×10−5 and 2.2×10−5Ω-m at room temperature and 77K, respectively, indicating weak carrier localization. The room temperature resistivities are 16% and 42% lower for WN/MgO(001) and WN/Al2O3(0001), suggesting a resistivity decrease with decreasing crystalline quality and phase purity.