Bill Fair and Earl Isaac created their first credit scoring system in 1956 and the FICO scoring system was first introduced in 1989. How did banks and lenders calculate credit risk and worthiness before these systems were in place?

Typically, Banks would use a process called manual underwriting. An underwriter would analyze your finances directly and rate your credit-worthiness. You would be rated based on bank statements, as well as other outstanding loans or lines of credit - the kinds of things that go into a credit score today.