Following the decriminalization of Christianity under the Edict of Milan in AD 313, Christians were prepared to build larger, more public worship spaces than had previously been used. In looking for a model, temples were rejected due to the darkness of the interior and their association with pagan religions. However, basilicas were deemed an acceptable model as they were not used for pagan religious functions. Early churches of this type followed the same basic plan as secular basilicas, with an altar replacing the throne at one of end of the basilica. Emperor Constantine ordered the addition of a transept perpendicular to the nave to create the form of a cross. The first of these imperial basilicas was St. John Lateran, which was given to the Bishop of Rome around the time of the Edict of Milan. These basilicas often stood behind an enclosed forecourt ringed with a colonnade or arcade. Today, churches in this style are referred to as architectural basilicas
The term “basilica” can also refer to ecclesiastical basilicas. These are large and important Roman Catholic churches which have been given special ceremonial rights by the Pope. The first of these were created in 1300 when Pope Boniface VIII coined the term “major basilica” for St. Peter’s Basilica and St. Paul Outside the Walls in Rome. This was a Holy Year, and pilgrims could gain an indulgence through visiting these two churches and confessing their sins. During subsequent jubilees, the title of major basilica was extended to St. John Lateran and St. Mary Major, also both in Rome, due to their historic nature as the cathedral of the Bishop of Rome and the oldest church dedicated to the Virgin Mary in Rome. In the 18th century, the classification of “minor basilica” was created as a way of designating important churches while distinguishing them from the four major basilicas. This designation is conferred only by papal brief and entitles the basilica to certain privileges including precedence over other churches in a diocese with the exception of the cathedral; the right to use the conopaeum (a baldachin resembling an umbrella) and a bell (called a tintinnabulum) during processions on important occasions; and the right to include the papal symbol of the crossed keys on banners, furnishings and the basilica’s seal. As of June 30, 2016, there are four major basilicas and 1,748 minor basilicas, the majority of which are in Europe and including 82 in the United States.