There are three branches of science of behavior analysis [i.e., experimental analysis of behavior, behavior analysis, and applied behavior analysis (ABA)]. ABA can be defined as a systematic approach to understanding behavior of social interest. For the past 40 plus years, researchers have evaluated ABA and ABA based procedures (e.g., behavioral intervention) as they relate to individuals diagnosed with autism spectrum disorder (ASD) and have implemented behavioral intervention in clinical settings for individuals diagnosed with ASD. In this paper, we discuss some of the pivotal contributions in the field of ABA in research and clinical practice. Additionally, we provide recommendations for the science and clinical practice of behavioral intervention in the next 40 years.