Yankee home runs against one team: 1956 and 2019.

The Yankees have four games remaining against the Baltimore Orioles in 2019, all in Yankee Stadium, which may be better for Baltimore. The Yankees hit five home runs in Baltimore tonight, bringing the total to 52 Yankee home runs off Orioles pitchers in 2019. This broke a Yankee record for most home runs against a team in a season: 48 against the 1956 Kansas City As. The As played in Kansas City 1955-1967, after Philadelphia and before Oakland.

In 1956 there were 8 teams in each major league, seven opponents, 22 games against each. In 2019 the Yankees and Orioles are in the same division and play 19 games against each other; 15 so far.

Here are the 1956 totals and those against the As, both in KC and in Yankee Stadium (YS) and those against the Orioles through Aug. 7, 2019, both in Baltimore and new YS.

1956	AB	HR	AB/HR
total	5,312	190	27.96
KC	764	48	15.92
in KC	405	26	15.58
KC in YS	359	22	16.32
2019	AB	HR	AB/HR
total	4,405	203	21.70
Balt	539	52	10.37
in Balt	375	43	8.72
Balt in YS	164	9	18.22

In 1956 Mickey Mantle had a major league triple crown, leading both leagues in:
HR: 52
RBI: 130
BA: .353

Mantle	AB	HR	AB/HR
total	533	52	10.25
KC	80	9	8.89
in KC	39	2	19.50
KC in YS	41	7	5.86

Mantle hit 10 home runs against both Cleveland and Detroit and 9 against the Washington Senators.

The designated hitter (DH) rule started in 1973, so Yankee pitchers batted in 1956. Three Yankee pitchers hit home runs in 1956:
Tommy Byrne: 3 in 52 AB; all against Detroit
Don Larsen: 2 in 79 AB; both against Boston; pitched a perfect game in the 1956 World Series against the Brooklyn Dodgers
Mickey McDermott: 1 in 52 AB; against Baltimore

The 2019 Yankees in 124 games already have more home runs than the 1956 Yankees had in 152 games.