40 home runs in a season with two different teams?

Answer 1

Through the 2008 season:

1) Mark McGwire - Oakland Athletics and St. Louis Cardinals.

2) Jimmie Foxx - Philadelphia Athletics and Boston Red Sox.

3) Alex Rodriguez - Seattle Mariners, Texas Rangers, and New York Yankees.

4) Ken Griffey Jr. - Seattle Mariners and Cincinnati Reds.

5) Jim Thome - Cleveland Indians, Philadelphia Phillies, and Chicago White Sox.

6) Johnny Mize - St, Louis Cardinals and New York Giants.

7) Greg Vaughn - Cincinnati Reds and San Diego Padres.

8) Albert Belle - Chicago White Sox and Cleveland Indians.

9) Shawn Green - Toronto Blue Jays and Los Angeles Dodgers.

10) Andres Galarraga - Colorado Rockies and Atlanta Braves.

11) Reggie Jackson - Oakland Athletics and New York Yankees.

12) Rafael Palmeiro - Baltimore Orioles and Texas Rangers.

13) Jose Canseco - Oakland Athletics and Toronto Blue Jays.

14) Rocky Colavito - Cleveland Indians and Detroit Tigers.

15) Manny Ramirez - Cleveland Indians and Boston Red Sox.

16) Jason Gianbi - Oakland Athletics and New York Yankees.

17) Gary Sheffield - Florida Marlins and Los Angeles Dodgers.

18) Darrell Evans - Atlanta Braves and Detroit Tigers.

19) Mike Piazza - Los Angeles Dodgers and New York Mets.