As this cartoon suggests, the Weather Underground's bombing of the U.S. Capitol on March 1, 1971 ushered in a new era in the minds of many Washingtonians. (Source: The Washington Post)

In the wee hours of the morning on March 1, 1971, a disturbing phone call came in to the Senate telephone switchboard. A man “with a hard low voice” told the operator that the U.S. Capitol would blow up in 30 minutes.

In the past, operators had fielded similar threatening calls from time to time, but all of them had turned out to be false alarms or pranks. This one, however, would be different.

True to the caller’s warning an explosion rocked the Senate side of the building at 1:32am. It was – as the Washington Post put it – the Capitol’s “sternest test since the British set torches to it in 1814.”

Fortunately the bomb went off in the middle of the night, so there were few people inside the building at the time and no one was injured. However, the device, which had been hidden behind a false wall in a ground floor bathroom, caused significant physical damage and was pretty unnerving to native Washingtonians and federal officials, alike.

In the days following the bombing, a radical leftist group called “Weather Underground” claimed responsibility for the bombing and promised more acts of violence to come: “We have attacked the Capitol because it is… a monument to U.S. domination over the planet. All over the country, revolutionaries are getting ready for the Spring. Our plans can be as creative and indigenous as the bamboo booby traps of the Vietnamese.”

Pretty scary stuff, to say the least. Anyone remember being in Washington when this happened?