Do a google search on photographing eagles in Iowa will bring up a lot of information on the locations as well as times. Depending on your location in Iowa, Clarksville, MO is a very good location.
We have some good spots in Des Moines, especially around Sailorville Lake and the mile long bridge. I've also seen some good shots in downtown around the Raccoon River.
Lock and Dam 14 in LeClaire, IA has a cement walkway/viewing platform below the dam. Eagles feed there alot and they are often hanging out in the tree's right next to the parking lot. I have had glass/lens envy everytime I've been there
I was there last weekend and had a great time photographing eagles in downtown Iowa City along the river, but my favorite spot was Coralville Dam. I stopped at dams 14 & 15 on the Mississippi and while there were 40-50 eagles at each spot, not a lot of great photo opps. Unfortunately, with temps now rising, peak eagle viewing is already starting to fade. The best time to go is during a couple weeks of frigid temps that freeze as much of the lakes and waterways as possible, forcing the eagles to congregate around the limited open water.
I agree with Iowa City and the Coralville dam. Downtown Ottumwa around the river has been a good spot as well if you're in that part of the state. My mother-in-law lived there and went eagle watching often.
