Nearly all of DC shut down for Trump's inauguration. So why was there no designated survivor?

The nation's capital was transformed seemingly overnight from a pedestrian-friendly city into a daunting and impenetrable fortress - the result of a multi-agency task force that erected 30 miles of anti-scale fencing, coordinated aerial surveillance and drones, and saw the deployment of tens of thousands of law enforcement, military personnel, undercover agents, and national guard trucks across D.C.

It's notable, then, that this year's sprawling security footprint did not expressly include one key component considered fundamental to U.S. tradition: The naming of a designated survivor.

In D.C., the tightly coordinated federal protection efforts were carefully planned long ahead of Trump's inauguration ceremony by the Secret Service and many other federal agencies. 

It's both a nod to recent security concerns, and more largely an effort to protect the U.S. body politic, foreign dignitaries, donors, and thousands of attendees from any mass catastrophe or threat. 

The designated survivor, who in a catastrophic event would bear the responsibility of leading the U.S. in the aftermath of a crisis, is typically a Cabinet officer when major security events put elected officials all in one spot, such as inaugurations and State of the Union addresses.

Previous designated survivors have included former DHS secretary Jeh Johnson, former Energy Secretary Rick Perry, and former Defense Secretary Robert Gates, who was tapped for the role during President Barack Obama's inauguration in 2009. 

The survivor's location, and sometimes identity, remains confidential until after the event disperses and its attendees have safely returned home. In high-profile events, a broader contingency plan is in place.

So it was notable that no designated survivor was named during the 47th presidential inauguration.

It's possible that the sprawling security presence coordinated in the run-up to Jan. 20 was deemed sufficient to protect against any threats.

It's also possible the event, which was held indoors and thus restricted to the public and to members of the news media, was limited enough as not to warrant the designated survivor. 

Ahead of the event, FBI and Secret Service personnel stressed the stringent security measures in place and the tight vetting of any ticketed attendees.

"All attendees will undergo screening," said Matt McCool, special agent in charge of the Secret Service's Washington Field Office. 

These individuals told Fox News that the fencing alone is more than any other designated National Special Security Event in the past.

"Designated checkpoints will be set up for members of the public interested in attending the inauguration," McCool said ahead of the inauguration - a protocol also applied to attendees of the modified Capital One festivities, which were moved inside due to frigid temperatures.

Fox News Digital's Elizabeth Elkind contributed to this report.