I-80 crosses the Sierra Nevada crest at Donner Summit (also known as Euer Saddle) at an elevation of westbound and eastbound. The Donner Summit Rest Area is located at this point. The summit is located in Nevada County, California. The pass is generally open year-round; it is plowed in winter, but may temporarily close during the worst snowstorms. The older, original US 40/Lincoln Highway route over Donner Pass is about two miles (3 km) to the south. This highway was replaced as the official trans-Sierra route by I-80 in 1964. Although the current Donner Pass is lower, Euer Saddle was chosen for the interstate because of more gradual approaches that aided construction to Interstate Highway standards, which do not allow the sharp curves used by the Donner Pass Road. The grade is 3-6% for 30 miles.