The yellow, black, white and red flag is the symbol of the American Indian Movement (AIM). The advocacy group was formed in 1968 in Minneapolis, Minnesota to address American Indian issues like sovereignty and treaties and Indian rights including Indian harassment and racism.
Indian, Objects - Misc
The signs at this roadside location say things like, "Their Children Prosper while Our Children Suffer", "Alcohol is the enemy" "Open eyes not cans".
Links: www.aimovement.org, en.wikipedia.org