When the dust settles, John Adams’s Nixon in China and Philip Glass’s Einstein on the Beach may stand as the most important operas of the latter twentieth century. The critical essay portion of this thesis examines the trajectory of minimalist opera, from its beginnings with Glass’s Einstein on the Beach through the more romantic operas of John Adams, Steve Reich’s multimedia opera The Cave, David Lang’s musical-influenced The Difficulty of Crossing a Field, and finally the post-minimalist operas currently being staged by young composer Nico Muhly. It examines the differences between the more abstract trajectory established by the early Glass operas and the plot driven trajectory established by operas more commonly associated with John Adam...