Longtime CBS News correspondent Mark Knoller has died at the age of 73.

He died in Washington, D.C., according to a close friend. The cause of death was not disclosed, but he suffered from diabetes and had been in ill health.

Knoller was, to put it simply, a legend. For decades, everyone in the White House press corps knew him as the unofficial presidential historian and statistician.

His frustration over the lack of a central database of daily presidential actions inspired him to take upon himself the enormous burden of keeping meticulous records of every presidential act, movement, and utterance, single-handedly filling an immense void in American history.

As he once put it: "I keep a daily log of everything the president does. I keep a list of speeches. I keep a list of travel – for

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