Morning Glory Pool before (left) and after (right) garbage thrown into the pool

Morning Glory Pool used to be clear blue in color, as shown in the historic undated photo on the left (National Park Service photo by Rentchler). However, close proximity to the road leading to Old Faithful (seen in the background of the photo on the right -- National Park Service photo by William Keller from 1965) meant heavy visitation, and tourists throwing so much garbage into the pool that the clear blue color was lost.