Merge queues have become an integral part of modern software development, evolving from niche solutions to an industry standard due to the increasing need for stable main branches amidst high PR velocities. Initially emerging from the challenges faced by early 2000s developers, such as Ben Elliston and later Graydon Hoare with the Rust project, these systems automated the process of ensuring a "green" main branch by testing PRs before merging. Early solutions like Bors and Homu set the foundation, which was further developed into tools like Bors-NG and embraced by large-scale organizations and platforms like GitHub and GitLab. These tools have automated PR merging, reduced manual intervention, and improved engineering efficiency, culminating in GitHub's native merge queue feature, which validates the approach and brings it to a broader audience. Despite some limitations in native options, third-party services continue to enhance functionality, demonstrating the critical role of merge queues in maintaining software quality and developer productivity.