You can sure tell that this station was owned by the same folks that ran KJR in its peak years, the 1960s:
In those days, KXL was a Portland station with 50,000 watts, but, according to Portland Radio Historian Craig Adams, was not allowed to operate after sunset from 1952 until 1980 to protect 1-A Clear Channel WSB in Atlanta.
Craig also mentions that, in 1959, KXL was one of five Top 40 stations in Portland. Going off the air at sunset was a distinct competitive disadvantage, and they soon abandoned the format.
Thanks to Portland's Mark West for digging this one out. As he points out, you just don't see this kind of promotion anymore.