Complex sentence: Of the 234,761 people of South America that arrived in the United States between 1820 and 1960, at least, some of them were Brazilian, already in 1960 the U.S. Census Bureau report counted 27,885 Americans of Brazilian ancestry.
Split into simpler sentences: Of the 234,761 people of South America that arrived in the United States between 1820 and 1960, at least, some of them were Brazilian. In 1960 the U.S. Census Bureau report counted 27,885 Americans of Brazilian ancestry.