After consulting my Nancy Drew Detective Manual and handwriting analysis kit (it was my sister's), I have come to the conclusion that it was written by a person with a determined mind, of moderate intelligence, with the objective of saying a lot without saying much of anything. He was probably right handed, walked with a limp, with thinning hair. He was of Average height and weight, give or take 6 inches and fifty pounds. Spoke with a southern Maryland drawl, and enjoyed fresh oysters. He had a suspicious nature, and was also somewhat paranoid. He possibly, could have been, indecisive by nature - maybe.
Based upon the writing style, I'd say it was likely written in New York sometime in March of 1865.
I need a larger handwriting sample to tell you more.