The A. M. Brown Union Executive Committee of Allegheny County Letter Book contains correspondence, announcements, news circulars, and voting forms. There is correspondence between committee members, soldiers requesting instructions for voting, appeals to citizens to vote Union, Simon Cameron correspondence, and requests from Joseph M. Wilson to A.M. Brown to pay the taxes of soldiers from Allegheny County so they would be permitted to vote.

Additionally, there are news circulars that encouraged the citizenry to vote Republican, notifications of soldiers coming to speak at campaign rallies, and blank forms for soldiers voting by proxy.