I was recently reminded, coming upon this and a couple of other covers/envelopes listed today, of the beauty of fancy old cancellation marks--and also how they bring a certain drama to whole face of an envelop, formally and informationally. Here I love the vertical stripes of the cancellation, blacking out the profile portrait of George Washington (like placing him behind bars), with this nice intersection of the red ring around him and the black ring of the postmark stamp just to the left. And then NEW YORK in bold black, with the year, 1861 printed upside down (which reads as 1981 right side up.) Maybe it's just me, but I find it all very tender and resonant. 

Of noble English descent, members of the Southworth family (a little research tells me) were among the early settlers at Plymouth colony. A direct descendent, Col. Consider Southworth (what an excellent name) was born in 1775 in Stoughton and went on to be a prominent shoe manufacturer and founder of a cotton-thread factory; I believe it is his son, Amasa, to whom this envelop was addressed. 

5 1/2" x 3 1/4" and in good overall antique condition, stains here and there, opened along the top.