This photo is dated march 3, 1926 Milford Delaware. The quality isn't that good but if you look closely you will see 3 martin houses. A magnifying glass brings out the details.
Two are on the vine covered pole in front of the house, right side, another one looks like it's hanging between the tree limbs.
I agree, probably didn't have martins, but who knows, maybe martins didn't mind a few trees 86 years ago.....landlords didn't have the PMCA
I think the two martin houses are actually mounted on a tree snag.
There may be another one just below and to the right of the house hanging between the tree limbs? It's on the vertical limb, looks like some type of feeder tray is up there on the right side also.
I have seen pictures on this forum of martins living in a house hanging from tree branches so it is not totally impossible. Especially back then when housing wasn't as plenty full. I don't know when they made the transition from holes in trees to man made housing but that picture was several generations ago so who know.