The Pentagon begins a major renovation to modernize its historic headquarters

In 1998, the Pentagon entered a comprehensive renovation period intended to modernize its aging infrastructure, improve workplace efficiency, and strengthen building security. Much of the original office space had consisted of large open bays ventilated through operable windows rather than centralized air-conditioning systems. Over time, these spaces had been subdivided into private offices, and individual air-conditioning units had become common. The renovation involved reconstructing interior spaces in phases, removing asbestos, sealing office windows, and introducing updated building systems. A standardized office arrangement known as the Universal Space Plan was also introduced, incorporating modern furniture and partitions. The project was particularly complex because the Pentagon continued functioning as the headquarters of the United States Department of Defense throughout the reconstruction process.