I sought the advice of the Transferware Collectors Club. Here is their response:
Hi *****,
Your pattern was made by Ralph & James Clews (1814-1834) around 1825. It is known as the States Series for the names of the States in the border (there are usually 15). Mainly, there is a different center on each size and shape, but the TCC database shows this pattern on a 12.5 inch platter. The scene is an English scene; Trematon Castle, Cornwall, but the interest is American because of the border, which also includes the words America And Independence, as well as a portrait of George Washington.