When the 1930s migrants Steinback based the Joads on reached Barstow, about two-thirds of them turned north to look for work in agriculture. The rest headed for Los Angeles, as did most post-World War II tourists. With so many people flooding into Los Angeles and few jobs to be found, the 1930s migrants didn't get a warm reception. For a few months in 1936, the Los Angeles police sent officers to the border with orders to turn back migrants with "no visible means of support." You can read about it here.
At Barstow, I-40 ends, merging with I-15 which follows Route 66 to Los Angeles, more or less.
Exit I-40 at Main Street to see Barstow's Route 66 landmarks. The unique McDonald's at 1161 E Main Street (at I-40) is more modern but fun - made from railroad cars - and it houses a small collection of vintage photographs.
Traveling along Main Street north, you'll pass old motor courts and motels including the El Rancho Motel (112 E. Main St.), built in 1943 from wooden railroad ties from the Tonepah & Tidewater railroad line.
A small detour on 1st Street across the railroad bridge leads to the Route 66 "Mother Road" Museum, housed in the restored Casa del Desierto, once a Fred Harvey hotel.