From the O'Reilly House Museum website:
The Father Miguel O’Reilly House is one of the oldest structures in St. Augustine, which makes it one of the oldest structures in the United States. The coquina and tabby portions of the building date to the First Spanish period (1565 - 1763). The Florida Master File puts the date of construction at 1691, and it is believed that during those 313 years, the property has only changed hands seven times (three of which were during the English period from 1763 - 1784). The artwork above is a detail of Father O’Reilly’s will pertaining to the O’Reilly House property, which he identified as the “stone houses with their orange groves,” which he bequeathed for the benefit of an order of female “religious educators according to the plan of Saint Francis de Sales.”
Since 1764, when Captain Lorenzo Josef de Leon (grandson of Joachim de Florencia, believed to be the original owner) sold the house to James Henderson, the owners of the house have been well documented. From the time Father O’Reilly purchased the property in 1785, the title to the property is unbroken and a matter of public record. Moreover, following the American Civil War, the physical appearance of the building is graphically documented in plan and elevation through photographs, drawings and maps.
As you step through the garden entrance you can clearly see that the original construction was influenced by the royal order of 1573. For defensive and security reasons, the decree stated that the main elevation of houses and gardens should be placed on the perimeter of streets. While the 1764 Puente map, a portion of which is shown on the home page, is the first documentary evidence showing a structure on the site of the O’Reilly House, archeological, historical and architectural evidence suggests that the house is from the same period as the Castillo de San Marcos.
Also from the O'Reilly House Museum website is the following information about the Sisters of St. Joseph:
The Father Miguel O’Reilly House has been a part of the lives of the Sisters of St. Joseph since the first eight Sisters arrived from the Motherhouse in Le Puy, France, amid the late summer heat of September 1866. The Sisters had volunteered to come to St. Augustine in answer to the call of Augustin Verot, then Bishop of Savannah, who had traveled back to his hometown of Le Puy the previous year. Verot wanted the Sisters to come to Florida to teach the children of the recently freed African-American slaves. The O’Reilly House, which by the time of their arrival had been held in trust for 54 years, became their first convent and first school.
Sixty-three years earlier, Father O’Reilly, then pastor of the St. Augustine parish, had the foresight to prepare a detailed will in which he left his residence, which had served as the parish rectory, for the benefit of an order of nuns “for education according to the plan of St. Francis de Sales.” (The Congregation of the Sisters of St. Joseph, though primarily based on the constitutions of the Society of Jesus, were influenced by the works of St. Francis de Sales.) The banner artwork on the page, “About the House,” is a detail of Father O’Reilly’s will in Spanish. The description speaks of “two stone houses with their orange groves.”
Upon Father O’Reilly’s death in 1812 the house was held in trust, first by his brother James, and then by the wardens of the parish. Ten years after the Sisters arrived in St. Augustine, Bishop Verot, who by this time had become the first bishop of St. Augustine in 1870, transferred the property cited in Father O’Reilly’s will to the Sisters of St. Joseph. Today they still hold the title.