P resident Donald Trump will observe the 24th anniversary of the terror attacks of Sept. 11, 2001 at the Pentagon on Thursday morning before traveling to New York. The administration is mourning the killing of conservative activist Charlie Kirk, who was fatally shot at a campus university event in Utah on Wednesday.

The number of total first responders and others diagnosed with 9/11-linked cancers has ballooned to 48,579 — a staggering 143% increase in five years, according to the latest data from the World Trade...