White Sox first baseman Paul Konerko will have to wait until Thursday to learn his fate as one of five players up for a fan vote for the final American League roster spot.
Thornton has been a reliable left-handed setup man and spot closer out of the White Sox bullpen this season, posting a 2.94 ERA with 47 strikeouts in 33 innings and a .195 opponents batting average.
Byrd makes his first All-Star Game in eight seasons. Signed as a free agent from the Texas Rangers before this season, Byrd is batting .310 with nine home runs and 35 RBIs as one of the few bright spots in an otherwise disappointing Cubs season.
"Today I got some good news," Byrd said before Sunday's game against the Reds. "It's been a long road for me. I've been on the ballot since '04. With the players voting me in, that's such a huge honor for me. They've seen what I've been doing this year, and they gave me this opportunity to represent the Cubs and the NL in the All-Star Game."
Konerko, a three-time All-Star who is batting .297 with 20 home runs and 57 RBIs, is up against New York Yankees outfielder Nick Swisher (.287, 13, 47), Minnesota Twins outfielder Delmon Young (.295, 9, 54), Texas Rangers third baseman Michael Young (.310, 11, 51) and Boston Red Sox first baseman Kevin Youkilis (.299, 16, 53).
Voting for the spot is under way at MLB.com and continues through Thursday.
Other Cubs who could have received consideration were closer Carlos Marmol, who has 15 saves in 18 opportunities and a .152 opponents batting average, and pitcher Carlos Silva, who is 8-2 with a 2.96 ERA.
"I'm a little sad that the two Carloses -- Silva and Marmol -- won't be out there with me, especially Silva. He is very deserving," Byrd said.
The pitchers and reserves for both teams were determined through a combination of player votes and selections made by All-Star managers Joe Girardi and Charlie Manuel.