Philadelphia appeared certain to set a daily snow record on Wednesday with a bona-fide rarity — a significant spring snowstorm that had a good shot at landing in the top 5 for spring snow.

However, the reign of the champ in the period of record — that would be April 4-5, 1915, when 19.4 inches was measured officially — remains secure.

>> MAP: How much snow has fallen around the Philadelphia region

And as bad as that was, it likely didn't measure up to the profoundly heavy snow of March 24, 1765.

Philadelphia has one of the nation's richest weather archives. The era of official government record-keeping dates to 1872. In terms of climate, however, researchers wouldn't mind having a few thousand more years in that database.

Figuring out what happened in the greater way-back requires some detective work and an acceptance of imprecision.

The North American natives encountered by the European settlers obviously had experienced some serious climate changes over thousands of years. Unfortunately, they did not leave much in the way of hard data.

It took a while for the New World settlers to start keeping score, but they did write things down, and journal and newspaper accounts provide some clues to major weather events.

The late weather historian David Ludlum dug out an item from the Pennsylvania Gazette, founded by Ben Franklin and published in Philadelphia, that discussed the storm of March 24, 1765.

Considering that it occurred in spring, "there fell the greatest quantity of snow that has been known," the paper wrote, up to 2½ feet, "and some places deeper."

This might sound familiar: "A great number of trees were destroyed by it, some torn up by the roots, others broken off. … The roads are rendered so bad and dangerous, that there was hardly any traveling since."

The storm temporarily halted one of the great measurement exercises in American history: the drawing of the Mason-Dixon Line along the Pennsylvania-Maryland border.

In their journal, Charles Mason and Jeremiah Dixon wrote that "at 9 a.m. snow was near 3 feet deep." For the next three days, they said, "snow so deep we could not proceed."