This Province is honoured by the fact that it is the Province of two great saints of the Church: Teresa of Jesus and John of the Cross. It was founded in 1416, when the Province of Spain was split into the two Provinces of Aragon and Castile. It was this Province which preserved the title and location of the ancient Province of Spain up to 1469. It included the convents of Toledo, Requena, Avila, Salamanca, San Pablo de la Moraleja, Santa Maria de los Valles, Gibraleon, Seville and Escacena, and, a little later, Ecija. In 1498 the four last mentioned houses were separated from Castile to form the new Province of Andalusia (Betica). The same thing had happened previously in 1425 when the convents of Moura and Lisbon, which belonged to Castile, gave rise to the Province of Portugal.

The Province remained relatively small, a situation which led St. Teresa to say that it was about to disappear. But later events have shown that the fear of St. Teresa was not well-founded, for in the years 1550-1557, the Prior General, Nicholas Audet, had included the Province among those which had accepted completely his reform, and which consequently grew in number of convents and religious, and, during the closing decades of the XVIIth century and through the following century, enjoyed its period of grand splendour. In the schools of the Province, which were affiliated to the Universities of Toledo, Salamanca, Alcala de Henares and Valladolid, many religious flourished in wisdom and virtue. Among these we recall especially the great mystic, Miguel de la Fuente and the great theologians, Pedro Cornejo de Pedrosa, Juan Bautista de Lezana and Luis Pérez de Castro. This Province, which through the centuries has given to the Order two Priors General, Juan González Feijoo de Villalobos (1692-1698) and Manuel Regidor y Brihuega (1825-1831), and fourteen bishops to the Church, also included the monasteries of nuns in Avila, Fontiveros and Piedrahita, founded at the end of the XVth and the beginning of the XVIth centuries. There were also two more monasteries of nuns founded in the XVIIth century in Madrid.

As was the case with all religious in Spain, the Province of Castile was suppressed by the government in 1835. The restoration of the Province began in 1948, when the Commissariat of Castile was established with houses in El Henar, Salamanca and Lomas de Zamora (Argentina). To these were added the houses in Madrid and Valladolid. The monasteries of nuns in Madrid (Maravillas), Piedrahita and Fontiveros, which managed to survive the decree of exclaustration, also belonged to the Commissariat. In 1984, Castile regained its status as a Province.