# Keystone

Keystone or key-stone may refer to:
* Keystone (architecture), a central stone or other piece at the apex of an arch or vault
* Keystone (cask), a fitting used in ale casks

## Companies

* Keystone Law, a full-service law firm
* Digital Keystone, a developer of digital entertainment software
* Keystone Aircraft Corporation
* Keystone Bridge Company, an American bridge building company
* Keystone (beer brand)
* Keystone Camera Company
* Keystone (gasoline automobile)
* Keystone (steam automobile)
* Keystone Pipeline, a crude oil pipeline
* Keystone-SDA/Keystone-ATS, a Swiss press agency
* Keystone View Company, a US photo agency
* Keystone (Berkeley, California), a defunct music club

## Education

* Keystone Academy, a private K–12 school in Shunyi, Beijing, China
* Keystone College, a private college in Pennsylvania, United States
* Keystone Exam, a standardized test at public schools in Pennsylvania, United States
* Keystone School, a private K–12 school in San Antonio, Texas, United States
* Keystone School Online, a private for-profit online K–12 school based in Herndon, Virginia, United States
* Keystone, an education program at the U.S. National Defense University

## Entertainment

* Keystone (video game), part of the Xbox Live Arcade title Fable 2 Pub Games
* Keystone (band), led by jazz trumpeter Dave Douglas
** Keystone (album), a 2005 album by the band
* Keystone Cops, a silent movie series
* Keystone Kapers, a classic Atari game
* Keystone Studios, a movie studio

## Places

* The Keystone asterism in the Hercules constellation

### United States

* The "Keystone State", nickname for the U.S. Commonwealth of Pennsylvania
* Keystone, Colorado, a town
** Keystone Resort, the related ski resort
* Keystone, Florida, an unincorporated community
* Keystone, Indiana
* Keystone, Iowa
* Keystone, Nebraska
* Keystone, North Dakota
* Keystone, Ohio
* Keystone, South Dakota, a town near Mount Rushmore
* Keystone, West Virginia
* Keystone, Wyoming
* Keystone at the Crossing, a business/shopping district in Indianapolis, Indiana
** The Fashion Mall at Keystone, located in the Keystone shopping district
* Keystone Heights, Florida
* Keystone Canyon, Alaska
* Keystone Lake, a resort area near Tulsa, Oklahoma
* Keystone, Wisconsin

### Canada

* The "Keystone Province", a nickname for the Province of Manitoba
** Keystone Centre, an arena and exhibition centre in Brandon, Manitoba

### Fictional locations

* Keystone City, home of the comic book character The Flash
* Keystone City, a holographic city in the Star Trek: The Next Generation episode "Emergence"

## Railroads

* Keystone Corridor, a rail corridor from Philadelphia to Pittsburgh
* Keystone Service, a current New York-Harrisburg service
** Keystone (Amtrak train, 1979–1981), a predecessor of the current service
* Keystone (Amtrak train, 1971–1972), a former New York-Pittsburgh service operated by Amtrak
* Keystone, a former New York-Washington service operated by the Pennsylvania Railroad
** Keystone (train), a lightweight train used for the service

## Sports

* Keystone Junior Hockey League, in Manitoba
* Keystone Cup, Western Canadian Junior "B" ice hockey championship
* Keystone (horse), a racehorse

## Other uses

* Keystone (limestone), quarried in the Florida Keys
* Keystone effect, caused by projecting an image onto a surface at an angle, or by photography at an angle
* Keystone Initiative, a medical protocol to reduce infection rates
* Keystone module, a type of data connector mounted in walls and patch panels
* Keystone Press Awards
* Keystone species, species that have a larger effect on their environment than is purely due to their abundance
* Operation Keystone, during World War II
* Keystone, a variety of screwdriver blade
* "Keystone", a descriptive reference to the Book of Mormon
* The Keystone, journal of the Pennsylvania Railroad Technical and Historical Society
* The Keystone, Pennsylvania news website owned by Courier Newsroom