1 Dec, 1974.
TWA514, a B727, diverted from KDCA to KIAD and was being vectored at 7,000 ft for a VOR approach to runway 12.
When the controller cleared them for the approach, they descended to and levelled at the FAF altitude of 1800ft.
They then flew into Mt Weather, about 20nm from the runway.
The accident report is worth a read, as existing misunderstandings between ATC and pilots regarding clearance terminology were uncovered and corrected.
To summarise, being cleared for an approach does not imply a clearance to descend from your current altitude, unless in accordance with a published route segment or as a part of further radar vectors.
As a result, since then, US ATC often say something along the lines of, “You are (distance) from (waypoint), maintain (altitude) until established, cleared for (approach type) to (runway).”
As several US lawmakers were killed in the crash, it served as a catalyst to develop the GPWS system.