The icon of Our Lady is an Odigitria icon (a Marian image meaning "She who shows the way"), that arrived in Kazan (800 km or 500 miles east of Moscow) from Constantinople in the 13th century. It disappeared in 15th century without leaving any traces.
According to a chronicle by Ermogen, Kazan's metropolitan (Orthodox bishop), the Virgin appeared to a girl called Matriona after the fire that destroyed the city in 1579 and told her where to find the precious image again. The once lost icon was placed in Kazan's Cathedral of the Annunciation.
An icon inspired by that of Our Lady of Kazan was sent in 1612 to Moscow to princes Minin and Pozharskij, who were leading the resistance against Polish invaders. The city's liberation on October 22 was attributed to the intercession of the Holy Mother of God of Kazan.
Later, the image became the private icon of the Russian imperial family. Czar Peter the Great brought it in 1721 to the cathedral of his new capital of Saint Petersburg.
In the early 1900s id disappeared again, stolen. Allegedly it was smuggled out of Russia and sold after the 1917 revolution for fear the new Communist regime would destroy it as it was doing with other religious artefacts.
A private collector bought a copy deemed the original in 1950 in England. The new owners offered it for sale to the Orthodox Archbishop of San Francisco (US Orthodox Metropolia or Archbishopric independent from Moscow since 1924)), who declined.
In 1964 the icon was shown at New York's World Fair after which it was bought by the Catholic Association Blue Army and donated to the Sanctuary of our Lady of Fatima in 1970. In 1993 it was given as a gift to the Holy Father who has kept it ever since in his private apartment in the Vatican. In his last meeting with the Pope Russian president Putin kissed it.
John Paul II has always wanted to return the icon to the veneration of the Russian people. The last scientific report by expert opinion confirmed its authenticity and dated it to around 1730.