Wheelchair vs the sidewalks

Hi y'all! I was wondering who we contact about the sidewalks Im a ambulatory wheelchair user and I've noticed how inaccessible some of the sidewalks are. Examples are the cracks in the sidewalks/un evenness of them or not having ramps at the end of the sidewalk which forces you to either get up out of your chair or go another way. I've seen a few people complain about them but I thought I'd ask!