We give an overview of the development of software model checking, a general approach to algorithmic program verification that integrates static analysis, model checking, and deduction. We start with a look backwards and briefly cover some of the important steps in the past decades. The general approach has become a research topic on its own, with a wide range of tools that are based on the approach. Therefore, we discuss the maturity of the research area of software model checking in terms of looking at competitions, at citations, and most importantly, at the tools that were build in this area: we count 76 verification systems for software written in C or Java. We conclude that software model checking has quickly grown to a significant field of research with a high impact on current research directions and tools in software verification.