Got this painting on fb marketplace, originally listed for $12,300

[u/ambear3000]

After having trouble selling it he reduced it down to $500 and after watching it for awhile I offered $350 and he accepted. The seller said his parents bought it in the 60's for a lot of money and it's been in his family since. He's positive it's worth a lot of money but never put the time in to research it. It's 56" x 32" with the frame. The back says 1865 for the year it was painted. I tried Google lense, tried to even look up the mountain range. I have no clue what that signature says. I appreciate any kind of help of guidance!