1920 city of Bisbee, Arizona.  This is one of two known varieties of porcelain plates from Bisbee.

1917 city of Argenta, Arkansas.  This plate is from what is today North Little Rock and is unique in collectors' hands.

1915 city of Little Rock, Arkansas.  Little Rock porcelains are known from 1909, 1910, 1911, 1915, and 1916.  This is the only 1915 known.

Undated city of Colton, California.  One of only two known, this Colton plate was probably not used on a passenger car.

1915 city of New Britain, Connecticut Milk Dealer.  The last in a series of New Britain Milk porcelain plates beginning in 1910, this plate (as are all the others) appears to be unique amongst collectors. 

1916 county of St. Lucie, Florida.  Although St. Lucie plates are known from 1913-1917, this is the only known passenger survivor for 1916 (one 1916 motorcycle plate is known).  This plate is one of more than 250 known porcelain prestates from Florida.

1914 city of New Orleans, Louisiana Motorcycle.  While there are undoubtedly others that exist, considering that New Orleans plates are not the rarest of city porcelains, I know of only two of these plates (Nos. 6 & 48).

1915 city of Ponchatoula, Louisiana.  A nice example of a one of a kind city porcelain from Louisiana.

1914 parish of St. John, Louisiana.  Another unique Louisiana city plate.

1916 city of St. Joseph, Missouri.  St. Joseph porcelains are known from 1913 to 1916.

1919 city of Rochester, New York Cartman.  Although confirmation is still lacking, conventional wisdom suggests that this and the numerous other New York Milk, Huckster, and Cartman plates that exist are from the city of Rochester.  Although the Cartman plates specifically are only known from 1918 & 1919, other examples of these Rochester varieties exist in porcelain from as early as 1909 to at least 1932.

1908 city of Columbus, Ohio.  Columbus issued porcelain passenger plates in 1907 and 1908, as well as a motorcycle plate in 1911.

Undated (1913-14) city of Muskogee, Oklahoma.  The second in a series of three porcelain plates issued by the city of Muskogee, this 1913-14 plate is one of only two known (Nos. 144 & 348) 

1914 city of Okmulgee, Oklahoma.  Although numerous Oklahoma prestates are known from various cities, this is the only one from Okmulgee.

1903 city of Philadelphia, Pennsylvania.  This plate has the distinction of being the earliest dated porcelain license plate of any kind known.  It is the first in a run of four porcelain Philadelphia city plates from 1903 to 1906.

Undated city of Gresham, Texas.  In the days before the state began issuing plates, automobile owners in Texas made their own plates.  One of the most common means of accomplishing this was to purchase "kit plates" like this one which were metal frames in which porcelain tiles would be fitted.

1916 city of Memphis, Tennessee Visitor.  From as early as 1914 to at least 1920, the city of Memphis issued both passenger and visitor plates.  This is the only known example of either variety from 1916.

1915 city of Seattle, Washington Commercial.  These Seattle commercial plates are known from 1914 and 1915.