Teakettle Junction is a well-known landmark encountered on Racetrack Road en route to The Racetrack in Death Valley NP. Visitors leave dozens of signed teakettles, but closer inspection reveals most are only a few months old. I’m not sure what the NPS does with all of them as they are collected.
There is also a lesser-known landmark a moderate distance to the north between Death Valley and Eureka Valley, known as Crankshaft Junction
. The artifacts there, however, have much lower turnover. They're heavy!