Before the 15th century prayer beads were used in various ways for the repeated recitation of simple prayers. During the 15th, the "Hail Mary" came to be the principal prayer for this sort of practice, supplemented in some places by meditations on the life of Christ. The same century also saw the introduction of the legend that the Rosary was originally given to St. Dominic by the Virgin Mary (Catholic Encyclopedia, s.v. "Rosary.") This supposed event became a popular subject in images of the ensuing centuries, in which we see Mary giving the Rosary to St. Dominic alone
(example) or along with other saints, as at right. St. Catherine of Siena is often among the other saints and sometimes the only one besides Dominic, as in the second picture at right.
Another type of Our Lady of the Rosary image is the one that prevails today. The Virgin Mary stands alone or with the Christ Child and holds a rosary in her hand, as in the third picture at right. There is very little consistency in images of this style, beyond the fact that the Virgin usually holds a rosary and wears blue and white.
The painting shown in the first picture at right has angels placing a crown on Mary's head. This is not very common in paintings, but the figures of mother and child often wear crowns in statues from the 16th through the 18th centuries (example). From the 20th, there is this stained glass with a crowned Mary giving St. Dominic the rosary.
In both types, the bottom of the image may portray souls in Purgatory awaiting the prayers of the faithful that will hasten their entry into Heaven (example).
By the 18th century (the time of the first picture on the right) the Rosary had evolved into the shape it has retained into the present: fifteen sets of ten recitations of the "Hail Mary" prayer, each set preceded by the Lord's Prayer, followed by the "Glory Be," and dedicated to one of fifteen events from the Gospels that in this context are called "mysteries" (Catholic Encyclopedia, ibid.). Some larger images may include panels portraying all fifteen events. The first picture on the right is an example; see its description page for an explanation of the mysteries.
Prepared in 2016 by Richard Stracke, Emeritus Professor of English, Augusta University