We find evidence of Portugal's devotion to Mary at the very beginning of her history. Soon after he became the first king of Portugal in 1139, Alphonsus I placed his kingdom under Mary's protection. In liturgical cult the Assumption held a place of singular honor. All of the cathedrals and some 150 parish churches are dedicated to our Lady under that title. Devotion to the Immaculate Conception was a later development. Father Ambrosio da Pina presents some excellent documentation whereby we can trace the origins of this feast in Portugal down to the beginnings of the 13th century.
Pina, A. Ambrosio de
"O início da Festa da Imaculada Conceição em Portugal na Peninsula Ibérica,"
Marian Library Studies:
Vol. 2, Article 7, Pages 86-89.
Available at: https://ecommons.udayton.edu/ml_studies/vol2/iss1/7