Alfonso John Romero is born in Colorado Springs, Colorado. His early exposure to computers sparked a lifelong passion for programming and game development. This early fascination with technology would lay the groundwork for his future success in the gaming industry.

Romero begins programming games on Apple II computers during his teenage years. This period of self-taught programming and experimentation solidifies his skills and fosters his creative approach to game design. He learned the fundamentals of game development, including graphics, sound, and gameplay mechanics, which were critical to his future work.

Romero gets his start in the gaming industry working at Softdisk. Here, he met future id Software co-founders John Carmack and Adrian Carmack. He works on several game projects and hones his skills in game development. This period was essential for him to develop as a professional game developer.

John Romero, along with John Carmack, Adrian Carmack, and Tom Hall, co-founds id Software. This marks a pivotal moment in gaming history. id Software would become renowned for developing groundbreaking first-person shooter games.

id Software releases Wolfenstein 3D, a groundbreaking first-person shooter that popularized the genre. Romero's design and programming contributions are significant to the game's success. Wolfenstein 3D set a new standard for fast-paced action and immersive gameplay.

DOOM is released, solidifying id Software's position as a leader in the first-person shooter market. Romero's level design and game mechanics contribute significantly to DOOM's immense popularity and cultural impact. DOOM’s multiplayer deathmatch mode was a major draw and laid the foundation for online multiplayer gaming as we know it.

Romero leaves id Software due to creative differences. This departure marks a significant shift in his career path as he begins to explore new ventures and game development projects.

Romero co-founds Ion Storm in Dallas, Texas, with Tom Hall. The company is highly anticipated, but their first major title, Daikatana, faces numerous delays and ultimately receives poor reviews upon release. This period is a critical point in Romero's career, highlighting the challenges of independent game development and high expectations.

Romero works on various game development projects after Ion Storm, including collaborations and independent titles. These ventures showcase his continued passion for game design and his willingness to explore new ideas.

Romero tries to launch the old-school FPS Blackroom, but the Kickstarter campaign faces criticism due to a lack of updates and overall communication. The project eventually is halted, and refund were given to backers. It is a mark of some of the modern-day issues in crowd funding game development.

Romero releases SIGIL, a free nine-level episode for the original DOOM, marking a return to his roots and a celebration of the game's enduring legacy. SIGIL provides a new experience for DOOM fans and demonstrates his continued passion for level design.

Romero released SIGIL II, another free episode for the original DOOM, continuing a return to his roots, following the success of the original SIGIL. SIGIL II expands on the DOOM universe that made him famous.