"Open range" means an area wherein livestock may lawfully be permitted to run at large.
In Harney County, Oregon where we have property there are many areas of "open range" on stretches of road. Knowing this we watch carefully when driving the roads. If there is a group of cows not far from the road you slow down because you never know when a calf could dart out onto the road. Most are easily shielded by the tall sage brush.
The last time I was in Princeton, I ventured out to the Round Barn Gift Shop and Museum 10 miles from our place. Most of the 10 miles are in open range. On the way back, I noticed a cow and calf standing next to the road. I slowed down and stopped. They were looking up the road and back toward me like we are all taught to look before crossing a street. I sat there smiling and waited. When they decided I wasn't going to move the calf ran across the road and the cow crossed in a leisurely fashion.