For the first time in 40 years, but only skipping one cycle that whole time, Iowa’s alphanumeric license plates have a Q as the first letter.
The 1986 series, which was issued during calendar year 1985, set the Q’s aside for Polk County. That was when counties were issued large chunks of sequences and you could nominally figure out which county a plate might be from from the letters. By the mid-’90s, many of those Q’s had probably been phased out, unless you kept the vehicle and/or kept plates when changing vehicles.
The 1997 series did not use D, I, O, Q, U, or V as first characters. The 2012 series, which we are going through right now, has used every letter of the alphabet so far as a first character. (Reports from license plate websites indicate that some of those six letters are not used in the second or third positions.)