ALPHONSO, the common English spelling of Affonso, Alonso and Alfonso, which are respectively the Galician, the Leonese and the Castilian forms of Ildefonso (Ildefonsus), the name of a saint and archbishop of Toledo in the 7th century.
The royal glass manufactory of La Granja de San Ildefonso was founded about 1725; in the first instance for the manufacture of mirror plates, but subsequently for the production of vases and table-ware in the French style.
The controversy with Spain was amicably settled by the treaty of San Ildefonso (1777); and further industrial and educational reforms were inaugurated, chief among them being the foundation, in 1780, of the Royal Academy of Sciences.
FERDINAND VII., king of Spain (1784-1833), the eldest son of Charles IV., king of Spain, and of his wife Maria Louisa of Parma, was born at the palace of San Ildefonso near Balsain in the Somosierra hills, on the 14th of October 1784.
In 1903, after the census had been taken, San Ildefonso (pop. 5326) was annexed to San Miguel.