The concept of the rearview mirror was first introduced by Dorothy Levitt in her 1909 book, *The Woman and the Car*. In 1911, during the inaugural Indianapolis 500 race, driver Ray Harroun became the first to mount a rearview mirror on a race car; however, its utility was limited due to severe vibration.
In 1914, Chester A. Weed obtained the first U.S. patent for a rearview mirror. During the 1920s, engineer Elmer Berger patented the "COP-SPOTTER" automotive mirror and began mass production, marking the official birth of the exterior rearview mirror for consumer vehicles. For a considerable period, rearview mirrors were often installed by owners as aftermarket accessories rather than being standard factory equipment; for instance, the 1937 Volkswagen Beetle did not come with a rearview mirror as standard. As vehicle speeds increased and road infrastructure developed, exterior rearview mirrors became increasingly common for safety reasons, eventually transitioning from optional accessories to standard factory equipment. It was not until the 1960s that rearview mirrors became mandatory under regulations in many regions. During this era, variations in regional traffic laws led to the emergence of "big-ear/small-ear" designs, featuring mirrors of unequal sizes on the left and right sides.
The 21st century has witnessed a major transformation in rearview mirror technology, shifting from optical to electronic systems. In 2016, the United Nations Economic Commission for Europe (UNECE) updated Regulation No. 46 (ECE R46) to permit the use of Camera-Monitor Systems (CMS)-or electronic rearview mirrors-as alternatives to traditional optical mirrors. On July 1, 2023, China's national standard GB 15084-2022, *Motor Vehicles-Devices for Indirect Vision-Requirements for Performance and Installation*, officially came into effect, establishing the technical standards and regulatory framework for the application of CMS in vehicles.
The development of electronic rearview mirrors continues as the technology permeates from high-end models into the mainstream market; however, the technology also faces challenges regarding user adaptation, costs, and technical reliability (such as image latency). Some automakers are using OTA updates to leverage existing surround-view cameras to implement "electronic side-mirror-like" functionality on the HUD, serving as a low-cost transitional solution.