Background and Context: Hour of Code is one of the largest educational campaigns implemented. It exposes millions of learners, to an hour of computer science fundamentals. With such a large impact, a large number of research articles have been published on the topic. This research ranges from reports of experiments testing the efficacy of Hour of Code and analysis of learner behavior, to reports of participation and suggestions for facilitating. Objective: The goal of this work is to determine the effects of Hour of Code on Computer Science education. Method: Articles in IEEE Xplore, ACM, EBSCO, ERIC, and Google Scholar that include "Hour of Code" were identified. Papers with "Hour of Code" as an emphasis of the research design or exploratory effort were analyzed. Findings: Systematic review identified 64 papers which were sorted into six categories. Papers focused on overall participation numbers to novel Hour of Code Activities and research using Hour of Code data. Implications: Analysis of these articles provides detail into the impact of Hour of Code on participants and influences resources for researchers. However, many questions remain to understand how Hour of Code can improve to meet its goals, expanding access to computer science to all students.