There were jewish enclaves but NYC did not see the overwhelming numbers until around 1890-1910. In 1880 there were 1.2 million people in NYC but only 80,000 jews most of whom came in the last decade or two. By 1910, the city had 4.7 million people, 1.2 million of which were jews. So it went from like 3% in 1850, to 6% in 1880, to 25% in 1910.