What were the requirements for citizenship in 1910-1920? Specifically, how soon after immigrating could someone begin the process, and how long would it take?

Canadian Citizenship wasn't established until 1947. Prior to that time, any British subject (those born in the UK, Canada, Australia, etc) was able to travel freely between British colonies without documentation. Those immigrating from other countries were naturalized, something they could apply for after living in Canada for a minimum of three years. For more information about this please see links