How did cyclists get over curbs before BMX era? There were curbs before 1970s, right? I wonder whether everyone had to dismount or dramatically slow down before curbs until bunny hop and wheel lift became popular, I guess, in 1970s among first BMXers. Same with cyclocross: for decades, from its beginnings, riders always dismounted before barriers. But suddenly, inspired by BMX, they realized it's possible to simply jump over?

EDIT: changed wording to underline that CX is much older than BMX.

EDIT2: I don't want to make you think that you need BMX bike to hop curbs. What I'm pointing to is that before BMX there was little mainstream attention to techniques like bunny hop (at least I got such impression), and after BMX got popular they spread throughout all cycling world. Though not many of us are skilled in jumping curbs, virtually everyone knows that can be done at ease by other riders.
People were doing tricks on bicycles almost as soon as they were invented. While I couldn't find references about curb hopping in particular, I'm pretty sure that these tricksters from the late 1800s wouldn't have had a problem pulling it off.  

Cyclocross has roots that go almost as far back. The first organized cyclocross races were around the end of the 19th century and the first French National Championship was in 1902.

I would guess that prior to BMX most people got over curbs the same way that most people get over curbs today. They slowed down a bit, lifted the front wheel over the curb, and leaned forward to get the weight off the rear wheel. Keep in mind, most cycling commuters can't pull off a decent bunny hop and many commuter bikes aren't designed to do so.