Complex sentence: By the late 1920s, the State of California began the first of numerous widening projects of what later became part of U.S. Highway 101; today the route through San Mateo and Santa Clara counties is designated as California Highway 82.
Split into simpler sentences: By the late 1920s, the State of California began the first of numerous widening projects of what later became part of U.S. Highway 101. Today the route through San Mateo and Santa Clara counties is designated as California Highway 82.