Altoona is a city in Blair County, Pennsylvania, United States. The population was 49,523 at the 2000 census, making it the ninth most populous city in Pennsylvania, after Philadelphia, Pittsburgh, Allentown, Erie, Reading, Scranton, Bethlehem and Lancaster. Altoona is located at 40° 30' 39" N, 078° 23' 59" W (40.510720, -78.399758).

Having grown around the railroad industry, the city is currently working to recover against industrial decline and urban decentralization over the past several decades. The city is home to the Altoona Curve baseball team of the Double A Eastern League, which is the Double A affiliate of the Pittsburgh Pirates. It also houses the 75+ year-old Altoona Symphony Orchestra, under the direction of Teresa Cheung. Prominent landmarks include the Horseshoe Curve, the Railroaders Memorial Museum, the Mishler Theatre, the Cathedral of the Blessed Sacrament, and the Jaffa Mosque.

Altoona is also the home of the Sheetz headquarters. Sheetz is one of the largest convenience store and gas station chains in the country, with more than 330 locations in Pennsylvania, Maryland, Ohio, West Virginia, Virginia, and North Carolina. Because of this, many Sheetz stores are located in and around Altoona.

A major railroad town, Altoona was founded by the Pennsylvania Railroad in 1849 as the site for a shop complex. Altoona was incorporated as a borough on February 6, 1854, and as a city under legislation approved on April 3, 1867, and February 8, 1868. The town grew rapidly in the late 19th century, its population approximately 2,000 in 1854, 10,000 in 1870, and 20,000 in 1880.

The demand for locomotives during the Civil War stimulated much of this growth, and by the later years of the war Altoona was known as a valuable city for the North. It was considered by Confederate General Robert E. Lee as a target during the Army of Northern Virginia's mid-1863 entry into Pennsylvania, before being repelled at the Battle of Gettysburg. Also notable is the Union's Loyal War Governors' Conference, held at Altoona's Logan House Hotel.

The Horseshoe Curve, a famous curved section of track owned by the Pennsylvania Railroad, has become a tourist attraction and National Historic Landmark. The Curve was used to raise trains to a sufficient altitude to cross the Allegheny Ridge to the west, beyond which was the steel town of Pittsburgh and the rest of the western United States. Because it was the industrial link to the western U.S., the Horseshoe Curve was a primary target of eight Nazi saboteurs who had infiltrated the United States during World War II (1942) by being dropped off by Kriegsmarine U-Boats.

In the early 20th century, the Railroad's Altoona Works complex employed, at its peak, approximately 15,000 people and covered three miles in length, 218 acres of yards and 37 acres of indoor workshop floor space in 122 buildings. The Pennsylvania Railroad built many of its own locomotives at the Works, some 7,873 in all, the last being constructed in 1946.

The Railroad had a significant influence on the city, creating the city's fire departments and relocating the hospital to a site nearer to the shop's gates. Today, the fire department employs 65 personnel and is the largest career department between Harrisburg and Pittsburgh, PA. The railroad sponsored a city band and constructed Cricket Field (a sports complex). In 1853, the Railroad built the Mechanic's Library, the first industrial library in the nation which exists today as the Altoona Public Library. With the decline in railroad demand after World War II, things began to decline steadily afterwards, with most of the plant is now gone. Many of the historic treasures of the city's history have also disappeared, including the aforementioned Logan House Hotel.

Altoona is one of the dual seats of the Roman Catholic Diocese of Altoona-Johnstown. The Cathedral of the Blessed Sacrament was made a cathedral and rechristened from St. John's Church in 1851.

The Altoona Mirror newspaper, founded in 1876 by Harry Slep, is Altoona's oldest media outlet. Today, the newspaper has a daily circulation of 32,000 and a Sunday circulation of 39,000. Approximately 13,000 people read the online edition of the newspaper each day.