Complex sentence: The older, original Lincoln Highway route (Historical US 40) 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.
Split into simpler sentences: 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.