The russians were able to establish a foothold in northern california (fort russ) because

No other European power had established a presence in the area.

In the early 19th century, Russia had already established some colonies in Alaska, securing its presence in America. Russia was expanding East, across Siberia, and eventually started moving south, until it reached Northern California.

Americans who were involved in the sea otter business proposed some joint hunting expeditions with Russian supervisors and Native Alaskan hunters to hunt seals along the Californian coast. These expeditions allowed the Russian parties to observe large stretches of uncolonized land. This led to the conclusion that a Russian settlement could be established in California.

especially research the treaty of greenville and the treaty of colerain in washington's administration.   also research at least one significant treaty from the administrations of adams, jefferson, and madison. tell the outcome of each treaty and how it did or did not in the further development of the west.

treaty of greenville (1814) the treaty of greenville (1814) was called a treaty of peace and friendship between the united states of america and the tribes of native americans called the wyandots, delawares, shawanoese, senacas and miamies.

the treaty of colerain was signed at st. marys, georgia in camden county, georgia, by benjamin hawkins, george clymer, and andrew pickens for the united states and representatives of the creek nation, for whom indian trader langley bryant served as an interpreter, on june 29, 1796, proclaimed on march 18, 1797, and codified as 7 stat. 56. colerain was a small community and the site of a u.s. indian factory founded by james seagrove.  

this treaty affirmed the binding of the treaty of new york (1790). the treaties of hopewell and the treaty of holston (1791) established boundary lines between the choctaws, chickasaws, cherokee, and the u.s. the treaty of colerain bound the creek nation to acknowledge the boundaries established in those treaties.  

it also established the boundary line between the creek nation and the united states. at the time of this treaty, the boundaries between spanish florida and the u.s. had not yet been established. this treaty formally allowed the creek chiefs to acknowledge the negotiation for delineating the georgia-florida boundary with spain.  

the treaty contained a provision that the president of the u.s. may establish a trading or military outpost.  

the united states demanded that the creeks give up their american prisoners and also return all "citizens, white inhabitants, negroes and property" taken by the creeks.  

the treaty describes when it would take effect. after the treaty had been signed but not yet promulgated, the u.s. senate requested modification of two articles of the treaty. the first modification stipulated that the military or trading posts would be under the control of the united states. the second modification stipulated that if the u.s. no longer required the use of those posts, the locations would revert to the creek people.