A portion of northwestern Nevada was imaged to determine the crustal structure and to assess reported differences between refraction versus reflection determinations of Moho depth and how the crustal composition and structure has been influenced by volcanic and extension mechanisms. Interpretation of the refraction/wide-angle reflection data suggests that the crust is fairly uniform in thickness and varies by less than 5 km over the 280 km east-west profile and 3 km over its 220 km north-south length. The velocity structure is characterized by five layers: 1) an uppermost crust, composed of sedimentary rocks and basement that has an average velocity of 5.7 km s-1; 2) a middle crust that extends to a depth of 18-22 with an average velocity of 6.1 km s-1; 3) a 10-12 km thick lower crust with an average velocity of 6.6 km s-1; 4) a 2-5 km thick transitional crust-mantle boundary defined by a 7.6 km s-1 velocity; and 5) an upper mantle with an average Pn velocity of 7.9-8.0 km s-1. A uniform upper mantle composition across the Basin and Range is suggested and the homogeneity of the velocity structure beneath the western Basin and Range argues for a youthful Moho and crust that has been reworked by province-wide late Cenozoic extension, episodic magmatism, and underplating. -from Authors