Russians in California

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The Russian advance in the central and western pacific happened during the 18th and 19th centuries , the plains Indians were already relishing the horse by then .

P.S. While visiting Australia ,the Russian explored Milukov-McKay tried to interest the Russian government in colonizing Papua New Guinea ,
thanks to his noble connections ,a couple of ships were send by the admiralty ,
their report was totally dismissive of the whole idea .

I believe Russian presence in Alaska began in the 1730s . As Sparky sez , horses were all over the western plains by then !

The Spanish and the Portuguese introduced horses to the Americas in the 16th century, with the Southwest and Plains Indians of North America transforming into horse cultures during the 17th century. The Cossacks were crossing the Urals and conquering (or, more often, claiming) Siberia for the Tsars in that same time frame.

It's not my understanding that Cossack troops were ever present in Russian America, which St. Petersburg considered to be little more than a backwater pelt-hunting ground.