And where there's protest, there's often law enforcement.
In accordance with inauguration protocol and in anticipation of demonstrations, Washington, D.C., was not short of security in its many forms.
Around 28,000 officials were employed as part of the inauguration's security plan. These included police from departments within and outside D.C., the Coast Guard, the National Guard, Transportation Security Administration personnel and Secret Service, Homeland Security Secretary Jeh Johnson said one week before the ceremony, NPR reports.
Here are 24 photos of just some of the inauguration's sprawling security plan in action.