The late Williams belted 521 homers and had a career average of .344. Yastrzemski won the Triple Crown for the Impossible Dream Red Sox of 1967, and became the first American League player to have 400 homers and 3,000 hits. Martinez won two of his three career Cy Young Awards with the Red Sox, and will be officially inducted into the Hall of Fame in July.
Ortiz played a pivotal role in guiding the Red Sox to their first three World Series championships since 1918, and is still going strong.
More than 10 million votes have been cast in the Franchise Four voting, and you can cast your ballot here. Voting ends on May 8, and winners from all 30 clubs will be announced at the 2015 All-Star Game, which will take place on July 14 at Great American Ball Park in Cincinnati.
Ian Browne is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.