California Highway 101 Marin-Sonoma Narrows Completion Ends 30-Year $1B Rebuild

The long-awaited Marin-Sonoma Narrows widening project on Highway 101 has officially been completed after 30 years of phased construction, addressing a notorious traffic bottleneck between Novato and Petaluma. The project added a third lane in both directions over a 16-mile stretch, creating a continuous 52-mile corridor of high-occupancy vehicle lanes from Windsor to the Richardson Bay Bridge, intended to ease congestion and support regional growth. Costing approximately $762 million for the Narrows portion and over $1 billion for the entire Windsor to Marin County border segment, the project reflects a blend of traditional road-widening solutions and forward-thinking multi-modal planning, incorporating the Sonoma-Marin Area Rail Transit (SMART) line and parallel bike paths. Officials emphasized the milestone's significance for local commuters and the region's economy, noting ongoing minor construction activities expected to conclude by November. The expanded freeway is anticipated to improve daily commutes and potentially increase tourism in Wine Country towns such as Petaluma. This successful infrastructure upgrade represents one of the largest public works undertakings in the area and a major step toward modernizing transportation in the region.