He was not the Mets' General Manager when the Mets became World Champions in 1969, but George Weiss deserves a lot of credit for putting together the Mets' first core of players.
Weiss already had experience with creating winning teams. He had been the Yankees' General Manager for years and the teams he put together won seven World Series championships. As a result, it was only natural that the Mets hired him prior to their inaugural 1962 season.
Although Weiss originally drafted many former Dodgers, Yankees and Giants players onto the 1962 Mets, he made two key trades before the season, acquiring Frank Thomas and Richie Ashburn.
Prior to the 1963 season, Weiss signed Ed Kranepool, Cleon Jones and Ron Hunt as the Mets' late-1960s core began to form. He later signed Bud Harrelson and Ron Swoboda as well. He also brought back the popular former Dodger, Duke Snider, for a victory lap season with the Mets.
In June of 1964, Weiss signed Tug McGraw as an amateur free agent, and two months later, he signed Jerry Koosman. He even got Yankees legend Yogi Berra to become a player/coach for the team, although Berra only had nine at-bats before retiring as a player and becoming a full-time coach.
In the 1964-1965 offseason, Weiss signed the legendary Warren Spahn who spent part of his final professional season with the Mets. After the 1965 season, he traded for another future mainstay in catcher Jerry Grote. He also acquired former MVP Ken Boyer from the Cardinals.
But Weiss' biggest move occurred in the 1965-1966 offseason. His assistant Bing Devine persuaded him to enter into the lottery for the rights of a college pitcher named Tom Seaver. Due to Seaver being rather unproven at the time, Weiss was at first reluctant to do so. But ultimately, he ended up placing the Mets in the lottery, and as fate would have it, the Mets won the lottery and Seaver became the new star pitcher for the team. This would become by far the greatest stroke of luck in Mets history.
Weiss also drafted a few other notable Mets during his time as General Manager, including Nolan Ryan, Ken Boswell and Duffy Dyer.