[Eternally Solo]

The last time foreign balloons were intercepted over US territory in April 1945 in Alaska. The balloons originated in Japan.

A hydrogen balloon with a load varying from a 33 lb (15 kg) antipersonnel bomb to one 26-pound (12 kg) incendiary bomb and four 11 lb (5.0 kg) incendiary devices attached, it was designed as a cheap weapon intended to make use of the jet stream over the Pacific Ocean and drop bombs on American cities, forests, and farmland. Canada and Mexico reported fire balloon sightings as well.

[kellyhound]

The Fu-Go.

Between November 1944 and April 1945, the Imperial Japanese Army launched about 9,300 balloons from sites on Honshu, of which about 300 were found or observed in the U.S. and Canada, with some in Mexico.

[William May]

The National Park Service posts warnings about these, showing up in isolated areas and still being lethal if they didn't explode when they landed. I think they estimated about 200-300 may still be out there.

[Eternally Solo]

Here is an interesting article about the bombing in Oregon ...

In 1945, a Japanese Balloon Bomb Killed Six Americans, Five of Them Children, in Oregon