Complex sentence: Horseshoe Lake is formed by Horseshoe Dam and was finished in 1946 upstream from Lake Bartlett, but unlike the other dams built to this point, the construction was done by the Phelps Dodge Corporation as part of a water exchange agreement.
Split into simpler sentences: Horseshoe Lake is formed by Horseshoe Dam and was finished in 1946, upstream from Lake Bartlett. Unlike the other dams built to this point, the construction was done by the Phelps Dodge Corporation as part of a water exchange agreement.