Oceanside is all about "101". The historic route, Highway 101, was constructed as the first modern road connecting San Diego with Los Angeles in the early 1900s. Following a similar route to El Camino Real (King's Road or Route) used by the Spanish padres in establishing 21 California missions that include the San Luis Rey Mission in Oceanside, signs of the 101 are everywhere. Sometimes you'll see banners on lamposts as you cruise along the historic highway. When you enter Oceanside and stop at the California Welcome Center, they sell lots of souvenir merchandise with 101 emblazoned on it.
And when you drive along 101 Highway that passes many businesses in Oceanside, you might do a double-take as you spot 101 Cafe with its colorful mural commemorating the Golden age of cars, California roads, carhops, and even golden French Fries. Inside, the authentic cafe serves the same great food that was cooked when Greyhound buses once stopped and let passengers off. The cafe also sells cool t-shirts, stickers, mugs, their own branded 101 stuff.
If you can count, take the 101, 405, 55 or 22 to connect with the 5 and head south to Oceanside in north San Diego County, where you will reconnect with the 101. It's a trip!