One day after hitting three home runs in Oakland’s 13 – 3 rout of the Indians, A’s rookie 1B Mark McGwire hits two more in a 10 – 0 Oakland romp to tie the major-league record of five homers in two games. McGwire’s nine runs in two games ties an American League record set in 1937.

On June 28, 1987 One day after hitting three home runs in Oakland’s 13 – 3 rout of the Indians, A’s rookie 1B Mark McGwire hits two more in a 10 – 0 Oakland romp to tie the major-league record of five homers in two games. McGwire’s nine runs in two games ties an American League record set in 1937.

Source
Baseball Reference June 28