Chapter 5

WordCamp US Philadelphia

Evolving Flagship Events

In 2015, the first national WordCamp US took place at the Pennsylvania Convention Center in Philadelphia, Pennsylvania. More than 1,800 WordPress users and makers attended.

WordCamp US was the evolution of the larger scope pioneered by WordCamp San Francisco. 2015 was the first official year of flagship WordCamps as we know them today.

By the time WordCamp US took place, there had already been 89 WordCamps in 2015, with more than 21,000 total attendees. Nonetheless, WordCamp US was the largest WordCamp that had ever taken place.

During the State of the Word address by WordPress co-founder Matt Mullenweg, Philadelphia Councilman David Oh declared December 5 ‘WordPress Day.’ Presentations ranged from sessions on security and accessibility to yoga and turning blogs into books.


Meanwhile, REST — REpresentational State Transfer — was a central topic in more than one session. The REST API merged with Core in WordPress 4.4, released on December 8, 2015, immediately after WordCamp US. This release, named “Clifford” in honor of Clifford Brown, integrated infrastructure for the REST API directly into the core.

Scott Taylor was the release lead for 4.4. “When WordPress adopts modern technologies, the Internet adopts modern technologies,” Scott said at WordCamp US. He was pointing out that the WordPress team had taken a position of leadership across the web.

REST API allows developers to access WordPress with JavaScript from outside the WordPress installation. APIs enable multiple systems to work together, and the REST API provides an interface for a variety of applications to access WordPress.

The REST API is the foundation for the block editor. It was available as a plugin before it was merged with Core, since that method of bringing in new features had been working well.


It was also the basis of Calypso, the open source project that allows users to manage both and Jetpack-enabled self-hosted WordPress websites using a desktop interface.

Calypso is a new interface for managing multiple WordPress sites and is written in JavaScript rather than PhP. Matt described it as the interface he would have built for WordPress in the first place if he had known then what he knew in 2015. While it’s often called “the new WordPress,” it is optional for (self-hosted) websites.

Jetpack must be installed on your website for Calypso to be available to you, and you must download the app. In January 2015, there had been just 71 contributors to Calypso. By November, there were 127. By spring of 2020, the number had grown to 496.

Calypso is now the standard interface for and is readily available for It allows quick management of multiple websites from the same interface.

As always, there were complaints. “I hope there is no plan or intention to delete the proper editor in favor of this terrible cut down version, clearly driven by the curse of the mobile phone,” wrote one commenter in a forum post about Calypso.

There was also excitement about the use of JavaScript. Matt, in his State of the Word presentation, reassured everyone: “PhP is not going away.”

Community Summit and Contributor Day

There was a Community Summit on December 2, Unconference Day, and on December 3. The Unconference day was a day of discussions with no slides, presentations, or electronic conversations. “The goal of the summit is to be honest and work through community issues without distractions,” says the website.

Contributor Day fell on Sunday, December 6. Teams included:
Core, led by Mike Schroder
Design, led by Mel Choyce
Accessibility, led by Rian Rietveld
Support, led by Jan Dembowski
Polyglots, led by Petya Rakovska
Documentation, led by Drew Jaynes
Theme Reviews, led by Tammie Lister
Marketing, led by Sara Rosso
Community, led by Josepha Haden
Meta, led by Ian Dunn
Training, led by Beth Soderberg

The next Community Summit would not take place until 2018 and then again in 2023. WordCamp US became an important annual event.