I got this from the book, "We, The Aliens". It's an introductory book to cultural anthropology.

Edit.

More can be written, but you might like to start with the FAQ page on North America, specifically 'How come America was not "discovered" via the Bering Strait?' by /u/Reedstilt. For when any part of the Far East became Russian, you might look for the mention of Dezhnev.

More was written. A few days later, /u/Searocksandtrees posted a list of links here. One dealt with the Russian state specifically (I linked to it too). Two others dealt with trade and travel with the area now called part of Russia.

This is not to discourage discussion. More questions, data and debate are welcome.