The San Luis Rey Bridge, which spans over the San Luis Rey River (and terminates right next to our house in Oceanside), was completed in 1925, open to the public in 1926. At that time, it was the largest bridge in the county. Just sixty years later, the bridge was too small and dangerous for modern traffic.
I remember when the San Luis Rey Bridge was the only bridge over the river. And I recall watching the new, extra long and curvy, Bonsall Bridge being built over the years in the late 80s/early 90s, while embarking on our weekly trips to the beach from De Luz. Caltrans actually wanted to destroy the historic San Luis Rey Bridge upon completion of the new Bonsall Bridge but the county stepped in (pushed by upset local residents) to protect and maintain the bridge. Since the completion of the Bonsall Bridge, the San Luis Rey Bridge became available for pedestrian/equestrian/cyclist use while simultaneously being designated a National Historic Place. Today is actually the first day I have ever walked across it, and I did it with my toddler, running along beside me.
The Bonsall Bridge is just 500 feet upstream from the San Luis Rey Bridge. It is neat too, just not historic (thankfully, since I saw it being built).