Gypsy is right. You should place yourself back in time and visulize were people then went and how they lived. The dirt was always there, you should look for where people played, went to church socials, had picnics, etc. The oldest parks are a good place to look, but they will also hold the most trash. Read all you can about the place near where you live, talk to old timey people.
Good Luck,
Sandman