Greencastle is a very small borough located in the state of Pennsylvania. With a population of 4,244 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 11.09% 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 overall education level of Greencastle citizens is substantially higher than the typical US community, as 29.25% of adults in Greencastle have at least a bachelor's degree, and the average American community has 21.84%.

The per capita income in Greencastle in 2022 was $47,218, which is wealthy relative to Pennsylvania and the nation. This equates to an annual income of $188,872 for a family of four. However, Greencastle contains both very wealthy and poor people as well.

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 Asian. 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 Arabic.