Boston, Massachusetts. Passenger Lists of Vessels Arriving at Boston, Massachusetts, 1820-1891. Micropublication M277. RG036. 115 rolls. National Archives, Washington, D.C.
A full list of sources can be found here
Information contained in the index includes given name, surname, age, gender, ethnicity, nationality or last country of permanent residence, destination, arrival date, port of arrival, port of departure, ship name, and microfilm roll and page number. If a name of a friend or relative whom the individual was going to join with, or a place of nativity was provided, that information is included in the index as well. Many of these items may be used to search the index in the search template above.
It is important to note that the port of departure listed on these passenger lists is not always the original port of departure for these individuals. A ship could make several voyages throughout the year, making several stops along the way. Oft times the port of departure found on these lists is the most recent port the ship was located at prior to arriving at the port of Boston. Therefore, if your ancestors emigrated to the U.S. from Germany, they could be found on a passenger list coming from Liverpool, England (if, in this case, the ship left from Bremen, Germany then continued on to Liverpool, England before arriving in Boston).
The microcopies of the passenger lists found at NARA are arranged chronologically by arrival date of vessel. If you do not wish to search this database using the search template, the images may be browsed following the chronological arrangement. To browse the images first select the "Year" in which you would like to search, followed by the "Month", and finally the "Ship Name".
To learn about researching in passenger records consult John P. Colletta's book, They Came In Ships (Salt Lake City: Ancestry, 1993).