The rural Plains have lost a third of their population since 1920. Several hundred thousand square miles (several hundred thousand square kilometers) of the Great Plains have fewer than 6 inhabitants per square mile (2.3 inhabitants per square kilometer)—the density standard Frederick Jackson Turner used to declare the American frontier "closed" in 1893. Many have fewer than 2 inhabitants per square mile (0.77 inhabitants per square kilometer). There are more than 6,000 ghost towns in the state of Kansas alone, according to Kansas historian Daniel Fitzgerald. This problem is often exacerbated by the consolidation of farms and the difficulty of attracting modern industry to the region. In addition, the smaller school-age population has forced the consolidation of school districts and the closure of high schools in some communities. The continuing population loss has led some to suggest that the current use of the drier parts of the Great Plains is not sustainable, and there has been a proposal - the "Buffalo Commons" - to return approximately 139,000 square miles (360,000 km2) of these drier parts to native prairie land.
how much of the population have the rural plains lost since 1920? 
a third

The palace, like Windsor Castle, is owned by the Crown Estate. It is not the monarch's personal property, unlike Sandringham House and Balmoral Castle. Many of the contents from Buckingham Palace, Windsor Castle, Kensington Palace, and St James's Palace are part of the Royal Collection, held in trust by the Sovereign; they can, on occasion, be viewed by the public at the Queen's Gallery, near the Royal Mews. Unlike the palace and the castle, the purpose-built gallery is open continually and displays a changing selection of items from the collection. It occupies the site of the chapel destroyed by an air raid in World War II. The palace's state rooms have been open to the public during August and September and on selected dates throughout the year since 1993. The money raised in entry fees was originally put towards the rebuilding of Windsor Castle after the 1992 fire devastated many of its state rooms. 476,000 people visited the palace in the 2014–15 financial year.
Since when have the palaces rooms been opened to the public?
since 1993

The Oak Street Connector (Connecticut Route 34) intersects I-91 at exit 1, just south of the I-95/I-91 interchange, and runs northwest for a few blocks as an expressway spur into downtown before emptying onto surface roads. The Wilbur Cross Parkway (Connecticut Route 15) runs parallel to I-95 west of New Haven, turning northwards as it nears the city and then running northwards parallel to I-91 through the outer rim of New Haven and Hamden, offering an alternative to the I-95/I-91 journey (restricted to non-commercial vehicles). Route 15 in New Haven is the site of the only highway tunnel in the state (officially designated as Heroes Tunnel), running through West Rock, home to West Rock Park and the Three Judges Cave.
Through what neighborhood in New Haven does Route 15 run?
West Rock