Marc Lowell Andreessen was born in Cedar Falls, Iowa, and grew up in New Lisbon, Wisconsin. His upbringing in a small town instilled a strong work ethic and a curiosity about the world beyond. This early environment, coupled with a natural aptitude for computers, laid the foundation for his future endeavors.

While working at the National Center for Supercomputing Applications (NCSA) at the University of Illinois at Urbana-Champaign, Andreessen, along with Eric Bina, co-created Mosaic, a revolutionary graphical web browser. Mosaic was user-friendly, accessible, and played a pivotal role in popularizing the World Wide Web among the general public. Its intuitive interface made the internet accessible to millions who had previously been excluded due to technical barriers.