The first three photos are of s/n 53-388, the first City of El Paso. The fourth photo is of the second B-52B with that name (s/n 53-0394). There is no indication what happened to the first. Click through for all the photos and info about the Ciudad Juarez.
The last photo is of the Ciudad Juarez. "This aircraft was accidentally shot down by a 188th TFS (New Mexico Air National Guard) F-100A on April 7, 1961, with the loss of three lives. Hard to believe, but an AIM-9 Sidewinder is capable of downing even such a large aircraft." More about this odd, tragic event can be found on this page.