After 1904, he pitched and managed in the minors for a few seasons, winning an International League pennant in 1905.

The Baltimore Terrapins played at their new steel-beamed modern stadium, Terrapin Park, which was across the street from his older "American League Park" of 1901 from the club's days in the beginnings of the "upstart" American League.

The team moved back to Baltimore in 1916, and Dunn again put together a juggernaut, ultimately signing 10 more players who went on to have solid major league careers.

By that time, Dunn's team was in the midst of winning seven straight International League championships, many by huge margins.

In addition to Grove, Dunn discovered other quality major leaguers such as Ernie Shore, Jack Bentley, Tommy Thomas, George Earnshaw, and Dick Porter.

It wasn't until the 1925 off-season, when the other, struggling teams in the league made an agreement with the majors on a set price for transferring players, that Dunn finally relented and began selling his stars for money.