In the late 14th century, as the persecution of Spanish Jews by their Christian rulers grew more severe, many fled to nearby Portugal. Many more would arrive after the expulsion of the Jews in 1492; only a few years later, however, the Portuguese monarchy forcibly converted its own Jewish population. As a result, crypto-Judaism persisted in Portugal much longer than it did in Spain. The historian Henry Abramson describes several weeks spent in Portugal on a tour of Jewish sites, and tells the story of the country’s Jews;

Portugal boasts an ancient Jewish settlement that reached a population of some 30,000 by the end of the 15th century. Perched on the edge of the Iberian peninsula, Portugal earned a reputation for tolerance that had long attracted Jews fleeing Spanish oppression, including [the 15th-century rabbi and diplomat] Don Isaac Abravanel’s grandfather Samuel, who fled the 1391 riots and forced baptisms [in Spain] to reclaim his Jewish faith in Portugal. . . .

In a break with Portugal’s history of relative religious tolerance, King João II initially refused to admit the estimated 100,000 Jewish refugees massing at his borders [in 1492]. Intensive petitioning finally moved the king to grant a six-month transit visa to 600 prominent families, at the exorbitant price of six cruzados per person (approximately $20,000 in contemporary currency). Despairing, many Jews chose to turn back, accept Christianity, and risk the depredations of the Inquisition. Others entered Portugal illegally, hoping to blend into the local population.

Both João and his successor Manuel I imposed harsh anti-Semitic decrees aimed at forcing the Jews to accept baptism, including the kidnapping of Jewish children and exiling them to São Tomé, a recently acquired island off the coast of west Africa; according to the historian Samuel Usque, himself a Jewish refugee from Portuguese persecution, nearly 2,000 of the 2,500 children abandoned on São Tomé died there, perhaps eaten by huge indigenous lizards. By 1497, the Portuguese persecution reached its nadir with the mass conversion of all remaining Jews, both Portuguese [natives] and Spanish refugees, such that the entire Iberian Peninsula was rendered [officially] Judenrein: free of Jews.

Amazingly, [these Jews] persisted. Traces of crypto-Jewish activity over the following centuries are recorded in Inquisition trial records and memoirs of those who managed to emigrate to safe havens like Amsterdam. [S]ecret traditions continued through the centuries, right up to the 20th century, when a Polish Jewish civil engineer named Samuel Schwarz . . . heard rumors of a Portuguese community that practiced Judaism in a tiny village called Belmonte. . . . Schwarz reported that the Belmonte conversos were skeptical that he was even Jewish. Only when he recited the familiar words of the Sh’ma prayer did they accept the fact that the Inquisition had not reached every living Jew.