But other plates are less innocuous.
Virginia — complying with orders from federal courts in 2001 and 2002 —makes its license plates available to the Sons of Confederate Veterans, whose logo incorporates the Confederate battle flag, a symbol of pride and heritage to some, a sign of racism to others.
And in Illinois last month, a federal district judge cited free speech when he ruled in favor of a group demanding that the state issue "Choose Life" license plates.
Backers say the message is intended to promote adoption; others say it's a thinly veiled political jab at legal abortion.
The ruling is on appeal, but more than a dozen other states already offer "Choose Life" plates.
Not surprisingly, supporters of abortion rights are trying to get a "United for Choice" plate approved in Florida.
The Illinois judge is just the latest to state the obvious: Once a state opens the door to using license plates to advocate a cause, it can't slam the door shut because the cause is unpopular or controversial. It's an all-or-nothing situation.
But "nothing" increasingly appears to be the smarter choice.
When specialty plates began to proliferate in the 1990s, the easy solution seemed simply to give everyone what they wanted.
However, states have since found themselves in the awkward position of trying to approve some groups' plates while blocking others.
What has evolved is a contentious political mess that has too often dragged through the courts. States that offer outside groups access to license plates almost inevitably find themselves enmired in draining controversies over abortion rights and racism.
And for what purpose? The specialty plates bring extra revenue into state coffers — and also into the treasuries of the sponsoring groups — but it's hardly enough money to compensate for the time wasted and acrimony caused.
If states stopped issuing any plates with advocacy messages — and that almost certainly would require eliminating the innocuous ones along with the politically charged ones — free expression wouldn't suffer. Drivers can, and do, put their opinions on license plate frames, bumper stickers, mud flaps and rear windows.
Lost in the angry noise over controversial messages is the purpose of license plates in the first place. The tags are supposed to show that a car or truck is legally registered, and to allow police or witnesses to identify a vehicle, sometimes in just a split second.
Drivers have every right to festoon their bumpers with Confederate flags, anti-abortion or pro-choice slogans and other political messages.
What they don't have the right to do is enlist the state to make its license plates another weapon in the nation's culture wars.