I am researching Russian visits to Alta California during the Mexican War of Independence, which were mostly or all projects of the Russian-American Company. There is a collection of Company documents in the U.S. National Archives, but it does not cover the crucial period during which Fort Ross was constructed (1812) and Russian sailors were detained by the Spanish administration (about 1815).
Apparently the company was headquartered in St. Petersburg during the relevant period. Is there an archive or library there in which records can be studied?