Coleslaw

If he has a tattoo he should be registered with the city. Call the city or SPCA and they will be able to find the owner.

I once found a lost dog at night and he had a dog license tag. I let him stay at my place for the night and the dog was able to return home the next day. Turns out the dog's home wasn't that close at all. Well it was not super super far, but I definitely wouldn't walk that distance.

Keep in mind you might think he belongs to a neighbour and lives close by, but you never know. I thought that dog must live close by too.
If you can't see the tattoo you can try just bringing him to a vet.