What was once unthinkable — is now a reality.

One million Americans have now died from the coronavirus, according to an announcement made Thursday by President Joe Biden, marking a long-dreaded milestone for an incomprehensible tragedy.

"Today, we mark a tragic milestone: one million American lives lost to COVID-19. One million empty chairs around the dinner table. Each an irreplaceable loss. Each leaving behind a family, a community, and a nation forever changed because of this pandemic. Jill and I pray for each of them," Biden said in a statement. "As a nation, we must not grow numb to such sorrow. To heal, we must remember."

The president plans to order flags to half-staff in remembrance.

Over the last two years, the deadly virus has kept the nation tightly in its clutch, with wave after wave of the virus washing over with only relatively brief respites in between.

“This unthinkable tragedy will forever appear in the history books,” said John Brownstein, Ph.D. an epidemiologist at Boston Children's Hospital and an ABC News contributor.

The loss of 1 million lives is a reality that is still difficult for many to comprehend, and to accept. In some respects, the death toll remains hidden from view.