Have to go with BOB2 on this, because I find the same thing looking through my ETTs, which for the Cal-P date from 1914. All the way up to 1941, the max speed permitted therein between Suisun and Davis was 60 mph until the mid to late 1930s, when it increased to 70 (in 1914 it was 30).

However, speed limit enforcement was rather lax until the Ricky Gates affair at Gunpow, which goes a long way toward explaining those old head stories of speed. Until Gunpow, how fast you were (oficially) permitted to go vs how fast you actually did were two vastly different things.

One other thing, all the old heads told me those daylight engines (4400s) were really bad steaming and riding; the 4300s on the other hand were dreams. One guy with a 30s date once told me that with a 4400, if you had the guts to take it above about 90, "it smoothed right out".