The Baltimore Blackbirds have been, for the most part, mediocre. Over half of their seasons have ended with a 3rd or 4th place finish, and they have only made the playoffs once. That was in 1915 before divisional play, when they won their only pennant and got their only championship, defeating the Eagles in the World Series. They have not been back to the playoffs since then (which means they are undefeated in the playoffs, although that doesn't say much since they have only been there once). They have a losing record all-time, but they do have a better overall record than five teams (only one of whom is an expansion team). They have good fan support, though, so they are likely to stay put long-term.
Fun fact: of the four players in the Hall of Fame with a Baltimore Blackbirds cap, three of them were on that 1915 championship team.

Best Season: 1915 (88-52)
Worst Season: 1930 (49-91)
Some notable players currently on roster