Clinton Leyard Blair, a business tycoon of the late 19th century, built his estate, Blairsden, in Peapack, New Jersey between 1898 and 1903. Blair was born into money, and like his father and grandfather, graduated from Princeton and went into business. He went on to establish the Blair & Company investment banking firm on Wall Street, was the governor of the New York Stock Exchange, and was director of the Millionaires Express. Blairs Millionaires Express was an extension of the Delaware and Lackawanna Railroad Line that extended into the western hills of Somerset County, New Jersey. This extension brought many wealthy families who worked in New York into New Jersey by easy, accessible transportation. Consequently many estates were built including Blairsden, which was constructed by architects Carrere and Hastings.

Blair lived at the Mansion with his family until his death in 1949. A year later the mansion and fifty acres were sold to the Sisters of St. John the Baptist for $60,000. After the mansion was bought in 1950 it was renamed St. Josephs Villa. The sisters remained in the house for many years.

The history of their stay has been considered mysterious by publications like Weird New Jersey, with speculation about a murder or series of murders at the mansion and questions about whether or not the nuns ran an orphanage or a hotel. These rumors have been put to rest through correspondence with a former member of the Sisters of St. John the Baptist.

St. Josephs Villa was run as a retreat house open to anyone who cared to visit. It was never operated as a hotel or orphanage, although in 1926 the order had purchased the Mosle Estate in nearby Gladstone, which was originally an orphanage. That property later became Mount St. John Academy. To the orphanage was added an elementary school and later a high school; the building for high school boarders became a site for marriage encounter programs, retreats, and conferences. The school buildings housing Mount St. John students later became a home for Montgomery Academy students.

The only shooting with even a distant connection to the Sisters of St. John the Baptist actually occurred at the James Pierpont Morgan mansion in Glen Cove, Long Island also owned by the same community. J.P. Morgan himself was shot in the leg at this estate, but the wound was not fatal. Sisters who made their novitiate there remember speaking of the "JP Morgan murder" which was a myth, since the famous millionaire was not murdered but actually died in Rome, Italy.

The Blairsden Mansion was built during the late-Victorian/early Edwardian era by Carrere and Hastings, who designed the New York Public Library. The Edwardian age of architecture has several distinct characteristics: brick exterior instead of wood or planks, use of concrete and steel, and contemporary technology (i.e., electricity).

Blairsden is measured at 26,000 square feet with 38 rooms. It contains 26 fireplaces, a pool, Turkish style baths, an indoor tennis court, a squash court, and halls perpendicular to the entrance connecting all the important rooms on the first floor.(2) The roof is slate and the exterior walls are made of concrete (30-inch thick) with an outer covering of brick. The secret of Carrere and Hastingss architectural style was to incorporate country estates into the landscape by rounding the roof to make it part of the surrounding hills.

The roof also reflects a style called Louis XIII, or according to several sources, French Eclectic. This is characterized by tall, steeply pitched roofs, eaves commonly flared upwards at the roof-wall conjunction, and brick or stone wall cladding.

Lastly the Louis XIII influence on Blairsden can also be seen in its amazing gardens, which were designed by James Greenleaf. The garden architect Greenleaf, who created the gardens surrounding the Lincoln Memorial in Washington, DC, used numerous fountains (including one of St. Joan of Arc), a reflecting pool, terraced areas of plant-life, and a cascading waterfall fountain. The estate, now estimated at $25 million, also contains a gatehouse, farm, and mile-long drive that ascends to the main entrance.