Roman Catholic immigrants came en masse to the United States around the 1840s and onward. A major reason for this influx of Roman Catholic immigrants at this time was the Irish potato famine in Ireland. Consequently, they were forced to leave Ireland to seek better prospects in America. With this, these immigrants brought their belief system with them, the Roman Catholic religion and its attendant practices.
By the year 1906, Roman Catholics in the United States were the biggest single religious denomination in the nation. At this time, Roman Catholics made up 17 percent of the total population. This represented 14 million out of 82 million people.
A major group of Catholic immigrants to British North America overall during colonial times was the group of Englishmen who arrived aboard the “Ark and the Dove.” These immigrants settled Maryland. Other Catholic colonists included some Germans who discovered religious freedom in Philadelphia and the State of Pennsylvania countryside.
However, as mentioned above, the Irish were a significant group of people who settled in the United States. The majority of Irish colonials were Scots-Irish Presbyterians. Nevertheless, several thousand Catholic Irish individuals additionally came and settled across the young colonies.
Again, the Irish potato famine was a major force of Roman Catholic growth in the United States. This famine occurred from 1845–1855.
The impact that these Roman Catholics had is that greater than 1.5 million Irish came to America in those trying years. The ranks of the Roman Catholic Church in Boston, Massachusetts; New York, New York; Philadelphia, Pennsylvania; and San Francisco, California increased to oblige these Irish believers who desired to hold to their Roman Catholic beliefs and traditions.