Currently, Squirrel Hill is a neighborhood in the eastern part of Pittsburgh, Pennsylvania and is bordered by Greenfield, Hazelwood, Glen Hazel, Swisshelm Park, Regent Square, Shadyside, Oakland, and Point Breeze. It's widely known for it's large Jewish population. It also contains a large amount of students due to the fact that Carnegie Mellon University has part of it's campus in Squirrel Hill and that Oakland, which contains the rest of Carnegie Mellon University and University of Pittsburgh, borders Squirrel Hill. By the locals it may also be called "Squill" which is just another Pittsburghese saying.
Squirrel Hill was named after the large population of gray squirrels in the area. In the 1760's, this area was a wooded hunting area just a little further east of Fort Pitt. Mainly Native American traders would hunt in this area. The first house, which still stands in Squirrel Hill today, was built by Colonel James Burd who was stationed at Fort Pitt. Mary Girty Turner, looking for her son who was abducted by Native Americans, settled in the Squirrel Hill area and two of her sons were the first to apply for land in the area.
In 1868, the forested 55 acre neighborhood was annexed to Pittsburgh, Pennsylvania after the Civil War. In the late 19th to 20th century, two large tracts of forests on the east and west were donated to Squirrel Hill. The western park was named Schenley Park and the eastern park, Frick Park.
Mainly, there were only a handful of roads connecting Squirrel Hill to Shadyside, Hazelwood, and the Monongahela shore. In 1893, there was an electric trolley that ran from Forbes Avenue into Schenley Park and then down Murray Avenue to Homestead. This caused Squirrel Hill to shift from being a neighborhood that faced the Monongahela river in the south to now face towards the north so that it could expand and reach towards Oakland.
In 1922, the Boulevard of the Allies was extended from Downtown Pittsburgh to Squirrel Hill, which caused a large jump in population until around 1927. The population increase was from Eastern European Jews moving from the Oakland and Hill District and into Squirrel Hill.
Squirrel Hill is still where about 47% of Pittsburgh's Jewish population lives. Present day Squirrel Hill has two city council districts, district 5 and 8, north and south Squirrel Hill respectively.
Sources:
http://www.orgsites.com/pa/shhs/_pgg6.php3
http://www.city.pittsburgh.pa.us/district8/html/squirrel_hill.html