The United States on Monday crossed the staggering milestone of 500,000 COVID-19 deaths just over a year since the coronavirus pandemic claimed its first known victim in Santa Clara County, California.

In a proclamation honoring the dead, President Joe Biden ordered the U.S. flag to be flown at half-staff on public buildings and grounds until sunset on Friday.

"On this solemn occasion, we reflect on their loss and on their loved ones left behind," Biden said in the proclamation. "We, as a Nation, must remember them so we can begin to heal, to unite, and find purpose as one Nation to defeat this pandemic."