Complex sentence: The competition from the Terrapins caused Dunn to sustain large losses; although by late June the Orioles were in first place, having won over two-thirds of their games, the paid attendance was as low as 150.
Split into simpler sentences: The competition from the Terrapins caused Dunn to sustain large losses. Although by late June the Orioles were in first place, having won over two-thirds of their games, the paid attendance dropped as low as 150.