This photograph shows a handsome gentleman photographed by Major Moulthrop, a famous photographer in New Haven, CT. Moulthrop was known as one of the first photographers in the area, and at his death was lamented as one of the oldest and longest in the photographic arts. The Photographic Times and American Photographer published an obituary of his death March 14, 1890. According to that publication Moulthrop took up photography sometime in the 1840s as a daguerrotype artist, and had previously been a landscape artist. Moulthrop lived 1805-1890. An advertisement for the studio from 1853 can be viewed here, and you will notice he was in the same building.
Concerning the subject of the photograph, I contacted a local history expert about his clothing. I have seen the stripe down the side of trousers worn by calvarymen, but I don’t know much about this as a fashion for men in general. It could have just been a fad, or this person could have been a retired calvaryman still using his old uniform pants. Hopefully I will hear back from the expert and be able to update you with some more information. Initially I thought the photo was from later in the century but the square corners belie the decade as the 1860s. He could be wearing his military style trousers as a badge of honor for service during the Civil War.
UPDATE: I heard back from my contact, a curator of many fine historical groups in and around Southern California. His opinion is that this is not a military person, but the trousers could in fact be military surplus. The style a la militaire was a fairly common fashion throughout the ages, so it is possible that this gentleman admired some famous US Calvary officer, or simply liked the combination of striped trousers and that style of facial hair. The remainder of the clothing is common civilian clothing, a morning coat, white shirt and striped tie.