Mary Ann Horton is a computer scientist, internet pioneer, and transgender rights advocate whose work helped shape both the early internet and the landscape of corporate LGBTQ+ protections. Best known for her contributions to the development of email and early UNIX systems, Horton was instrumental in expanding how computers communicate—long before Gmail or Slack existed. In fact she was instrumental in the adaptation of @ in emails.
Mary Ann Horton was born in Richland, Washington in 1955 and discovered a passion for computer programming early on. She earned her bachelor’s degree in computer science from the University of Southern California in 1976, followed by a master’s at the University of Wisconsin. In 1978, she transferred to the University of California, Berkeley, where she completed her PhD in computer science in 1981.
While at Berkeley, Horton’s dissertation focused on developing a new kind of syntax-directed editor—a tool that understands the structure of programming languages and helps developers write code more easily. This early work laid the groundwork for what would later become computer-aided software engineering (CASE) tools, which are used to speed up software development.
During her time at Berkeley, she also contributed to Berkeley UNIX, one of the most influential early operating systems. She worked on the vi text editor, which is still used by programmers today, and created uuencode, a tool that made it possible to send binary files like images or programs over plain-text systems like email—something that wasn’t possible before.
In 1981, Mary Ann Horton joined Bell Labs in Columbus, Ohio, as a Member of Technical Staff. There, she helped bridge the gap between Berkeley UNIX, an advanced research-focused computer system she had worked on during her PhD—and UNIX System V, the commercial version used by businesses. She brought over essential tools like the vi text editor, which let users write and edit code efficiently, and curses, a software library that made it possible to build more interactive, text-based computer interfaces in an era before graphical screens. She also developed terminfo, a system that helped programs run smoothly across different kinds of computer terminals. This upgrade replaced an older, less flexible system called termcap, and her solution became a standard feature in UNIX systems still in use today.
By 1987, Horton had joined the Bell Labs Computation Center, where she focused on introducing Usenet and email into the organization’s infrastructure. At the time, internet access wasn’t yet widespread, so digital communication relied on tools like UUCP (UNIX-to-UNIX Copy Program). UUCP let computers send messages and files to one another by passing them along through a chain of connected machines—kind of like a relay race. It wasn’t instant or seamless, but it allowed people to share information across long distances, even without a direct connection between their systems.
Horton played a key role in expanding and organizing this early communication network. She made UUCP easier to use and more reliable, and she helped connect major early networks like ARPANET (the government’s precursor to the internet) and Usenet (an early public online forum). These systems weren’t originally designed to communicate with each other, but Horton helped build the bridges that allowed them to work together.
Her efforts didn’t just improve technical performance—they helped grow email and message-sharing into something global and foundational. Horton continued to support Usenet through 1988, shaping its infrastructure, helping it scale, and laying the groundwork for the kinds of digital communication systems we rely on every day.
Beyond her work in computing, Horton is also a consultant on transgender workplace inclusion and UNIX and internet technologies. She owns Red Ace Technology Solutions, a company that offers affordable web hosting to small businesses and nonprofits.
After transitioning in the late 1990s, she began advocating for transgender rights in corporate environments. At Lucent Technologies, she successfully pushed for the addition of gender identity to the company’s nondiscrimination policy in 1997—the first time a major U.S. corporation had taken that step. She also worked to secure inclusive healthcare benefits for transgender employees, helping to open doors long before these conversations became part of the national dialogue.
In her 2022 memoir, Trailblazer: Lighting the Path for Transgender Inclusion in Corporate America, Horton reflects on her journey as a technologist, activist, and trans woman. Her story is a reminder that innovation isn’t just about the systems we build—it’s also about creating space for everyone to thrive within them.
