Greencastle is a very small borough located in the state of Pennsylvania. With a population of 4,226 people and three associated neighborhoods, Greencastle is the 360th largest community in Pennsylvania.

A relatively large number of people in Greencastle telecommute to their jobs. Overall, about 10.97% of the workforce works from home. While this may seem like a small number, as a fraction of the total workforce it ranks among the highest in the country. These workers are often telecommuters who work in knowledge-based, white-collar professions. For example, Silicon Valley has large numbers of people who telecommute. Other at-home workers may be self-employed people who operate small businesses out of their homes.

The education level of Greencastle citizens is substantially higher than the typical US community, as 33.49% of adults in Greencastle have at least a bachelor's degree.

The per capita income in Greencastle in 2022 was $50,681, which is wealthy relative to Pennsylvania and the nation. This equates to an annual income of $202,724 for a family of four.

The people who call Greencastle home describe themselves as belonging to a variety of racial and ethnic groups. The greatest number of Greencastle residents report their race to be White, followed by Black or African-American. Important ancestries of people in Greencastle include German, Irish, English, European, and Scots-Irish.

The most common language spoken in Greencastle is English. Other important languages spoken here include Spanish and Polish.