The Tomcat projects started at Sun Microsystems as the reference implementation of the Java Servlet and Java Server Pages Specifications. The Java Community Process (JCP) site contains all the details of those specifications.
The Tomcat code base was donated by Sun to the Apache Software Foundation in 1999, and the first Apache release was version 3.0. Since then, multiple volunteers from Sun and numerous other organizations have contributed to the product. There have been multiple major releases and the product has enjoyed considerable industry adoption as well as a healthy and active community.
In 2005, Tomcat became its own top-level Apache project, leaving the Jakarta umbrella and oversight structure to manage itself.