From: 'St. Peter's - Guide to the Basilica and Square'
The altarpiece, by Pietro Bianchi (1694-1740), shows the Virgin Immaculate in glory surrounded by angels and venerated by Sts. Francis of Assisi, Anthony of Padua, John Chrysostom. On December 8, 1854, on the occasion of the proclamation of the Dogma of the Immaculate Conception, Pius IX crowned the image of Mary. To mark the 50th anniversary of the Dogma, St. Pius X added a second crown, consisting of twelve stars, gleaming with twelve brilliants, donated by various nations.

Beneath the altar are the remains of St. John Chrysostom and relics of St. Francis and St. Anthony. The paschal candle stands on a black and white marble column with a porphyry base, in accordance with Paul VI's wishes.

From: St. Peter's Basilica - A Virtual Tour' by Our Sunday Visitor
Both were designed by Carlo Maderno, who in 1607 supplied the drawings for this one, also called Sistine because it took the place of the one which Sixtus IV had built and consecrated, and where he was later buried in the superb funeral bed by Pollaiolo, commissioned by his nephew Giuliano della Rovere, who later became Julius II.

The old 15th century chapel was dedicated to the Immaculate Virgin and to St. Francis of Assisi (Sixtus IV was a Franciscan) and St. Anthony of Padua. The decoration of the present Chapel started in 1622 under Gregory XV, as is inscribed in the base ring of the lantern.

The Virgin Mary in the altarpiece was crowned with a golden diadem by Pius IX on Dec. 8, 1854, the day on which he decreed the dogma of the Immaculate Conception. Later a crown of diamonds was added, donated in 1904 by an international committee of ladies.

From: 'The Mosaics of Saint Peter's' by Frank DiFrederico
Pietro Bianchi received his first payment for the picture that served as the cartoon for this mosaic in 1734. However, the Fabbrica did not receive the picture until somewhat later. In 1738 Bianchi was paid another 200 scudi for the painting, with the condition that he finish it within one year, but apparently it was only barely finished at the time of his death in 1740. The final payment for the painting was made to Bianchi's heirs in the summer of 1741. The mosaic was executed by Nicolo Onofri, Enrico Enuo, Giuseppe Ottaviani, and Guglielmo Paleat from 1744 to 1747. The painting by Bianchi is now in S. Maria degli Angeli, Rome.