Check out 'East of the Sun'. It is a history of Russian conquest of Siberia from the middle ages to Soviet times.

http://www.amazon.com/East-Sun-Conquest-History-Siberia/dp/1880100851

Quoting myself from here.

Read Glorious Misadventures by Owen Matthews. It goes into detail the whys and hows of Russian Eastward expansion, and how they got all the way to northern California before America did. (Their explorers actually sailed by the Lewis and Clark expedition.)

The reason? Furs.

Russia made some ridiculous amount of money in the fur trade. Rezanov's company (the Russian-American Company, similar to the Dutch East Indies Company, etc.) was responsible, alone, for something like 15% of the entire GDP of Russia during the early 1800s.

The fur trade was ridiculously profitable, but the down side was that they were driving all the fur species extinct from over-trapping. So they pushed further and further east to follow the furs, eventually crossing over into Alaska and then down into California. They tried expanding to Hawaii as well (with disastrous results) and tried to open trade with Japan (with disastrous results), and tried to move inland in Alaska (with disastrous results), so they eventually (after a long period of time) gave up and sold it to America.

The early expansion was pushed by groups called Cossacks ("free men"), which came from the western/southern Russian, Ukrainian, and Polish regions, in search of land and money with little oversight. They moved east, river system by river system, conquering the native tribes, building fortified emplacements, and engaging in the fur business. They moved along a spectrum of {alliance of equals} to {subject protectorate} to {imperial subjects} with Russia over the years.

hi! you may be interested in some previous posts on the topic

(in no particular order):

• How did the Russians conquer Siberia? How long did it take them?

• How did Russians interact with and assimilate the native cultures in Siberia during eastward expansion in the seventeenth and eighteenth century?

• Historically speaking was Siberia "empty" of peoples or at least people that kept records prior to Russian expansion?

• What were the motivations behind the Russian conquest of Siberia?

• How much control could the Tsar exert over eastern Siberia, ~8000 km away, in the 17th century?

• A Russian Louis and Clark?

sources

• Sources for history of Siberia and Russia's Far East? Very Early to Middle Medieval times? History of Khanates, tribes and people in the area?

• How did Russia go about taking control of Siberia