Claim: The 1970 San Francisco 49ers season was the team's first in the NFL, and in the preseason they won only a single match, against the Denver Broncos.
Evidence: The 1970 San Francisco 49ers season was the franchise's 21st season in the National Football League, and the 25th overall. The National Football League (NFL) is a professional American football league consisting of 32 teams, divided equally between the National Football Conference (NFC) and the American Football Conference (AFC). 
San Francisco 49ers 1946 (AAFC), 1950 (NFL) First season