me and sharon went to a historical military site along the penobscot river today. as i was walking the trail along the river i noticed a whole hedgerow of thornless red stemmed dark green glossy leaved canes. i thought they were wild black cap raspberries but on closer inspection they were blackberries! in all my travels in maine I’ve never seen a wild growing blackberry in this state! of course i had to take some stealthy cuttings and dug a few shoots as best i could. the fruit weren’t much bigger than a raspberry but the bushes were loaded with the most amazing tasting blackberries I’ve ever tasted!! when i got home, i quickly planted my cuttings and the few sprouts i managed to collect. i sure hope some take! I’m going to make a new patch just for them ! its like i hit gold or something! 
Thornless? Isn’t that pretty rare in the wild?
Yes, although there is precedent for it. They might also be feral berries. Regardless, it’s a great find and a fun mystery. 
In Maine that is gold but thornless in addition is like platinum!
We have wild blackberries growing along my runnings trails here in Downeast Maine but not thornless. Nice find!
i found these at ft. knox state park. the history says this fort was manned by troops from Ct. during the civil war. maybe it was transported there and naturalized? i take the thornless back . they have about 1 thorn every 12in. and the thorns are as big as a raspberry thorn. very tiny and almost unnoticeable. i picked several handfuls of the berries and didn’t get a scratch. after finding that patch i kept a eye out for others and didn’t see anymore. found them on the trail back up the hill from b battery if anyones interested. id like to see someone develop superior cold hardy blackberry from these. this area is in zone 5a but in a exposed area near the river so probably at least zone 4 hardy.
how big are the fruit on the ones along your trails? I’ve heard they were growing wild down your way but I’ve never come across them.
The fruits on the blackberries her in Downeast are pretty small. I’d say similar in size to a raspberry, just like yours. They have a great flavor though!