What led to the change for cleaner streets/public places – and why does it appear as if we’re reverting to our former messy ways?

Question

In “historically accurate” movies/period pieces or drawings, paintings, or pictures of the same time – say a few hundred years ago (picture NYC or London in 1820), the streets and river shorelines, etc. are portrayed as dirty, unclean, filthy, messy, (insert your own adjective here). What led to the change for cleaner streets/public places – and why does it appear as if we are reverting to our former messy ways?

In: Other

Answer 1

Cars.

Cars were the “solution” to the “horse pollution” problem. Cars led to curbs and pavement. Pavement was easier to clean, and that led to street sweeping machines.