Congress enacted the first legislation concerning the processing of immigrants in 1819. It provided that a record should be kept of the number of passengers in each customs district and mandated the registration of each person's name, age, gender, occupation and country of birth. Up to 1867, the records included all "alien passengers arrived" and did not distinguish "immigrants" from "passengers."
Beginning in the 1830s, the tide of immigration tripled and quadrupled the numbers of previous years. This was due to a large increase in German and Irish immigrants. Many "German" political refugees and intellectuals fled their native lands. They had no "German" passports, because "Germany" did not yet exist as a nation, so these immigrants had passports of their various states, such as Prussia, Bavaria, Saxony, and Wurtemberg.
From 1800 to 1845, the Irish population grew with abnormal rapidity. The standard of living became so low that a large proportion of the population subsisted almost entirely on potatoes. The potato blight ruined the crop three years running, from 1845 to 1847, and half a million people died from starvation, typhus, and cholera. Millions more were barely kept alive by soup kitchens and limited aid, much from America. These conditions prompted a mass exodus of immigrants.
The 19th century was the apex of the Golden Age of Sail (1460-1860). Many types of sailing vessels carried immigrants to America. Due to the prevailing westerly winds, the passage from Europe to the United States averaged four to six weeks and included crowded, noisy, smelly, vermin-ridden confinement. Considering the appalling conditions, a total absence of hygienic facilities, questionable food, stale water from oaken casks, and no medical care, the wonder is that more did not die at sea.
The "denomination" listed in the database is the type of vessel (ship, brig, schooner, etc.) and is not part of the ship's name (ship's names include Commerce, Rose in Bloom, Boston, etc.).
shipA vessel of at least three square-rigged masts; averaging 500 tons; 130 feet in length; 30 feet in the beam.
bark or barque A three-masted vessel with the fore and main masts square-rigged and the rearmost fore and aft rigged; slightly smaller than a ship.
brigA vessel with two masts, fore and main, with square-rigged sails; averaging 250 tons; 190 feet in length; 25 feet in the beam.
schoonerA vessel with two or more masts, fore and main, with square-rigged sails; averaging 100 tons; 68 feet long; 23 feet in the beam; the largest ever built had seven masts.
sloopA small, single-masted vessel, fore and aft rigged, with a main sail and a jib; from schooner size downward.
packetA boat, of any kind, that travels a regular route along a coast or river, carrying passengers, freight, and mail.