Unsorted Christmas mail for the American Expeditionary Forces at Pier 86 in New York in November 1918. (U.S Army Photo/Interim Archives/Getty Images)

People line up at the parcel post window at the General Post Office to mail their Christmas packages, in New York on Dec. 22, 1927. (Underwood Archives/Getty Images)

According to Sue Brennan of the U.S. Postal service, USPS estimates that it will deliver more than 750 million packages between Thanksgiving and Dec. 31 this year. FedEx projects a record-breaking  370 million; UPS predicts the service will deliver more than 700 million.

For a country of only about 325 million , that means mailrooms across the country and postal workers worldwide will handle more than five packages per American this holiday season.

In recent years, this influx has been credited for the rise of online shopping, but as history shows us this surge in mail is as much a holiday tradition as mistletoe and mulled wine.

Even during wartime, the U.S. Postal service — one of the few governmental agencies explicitly mentioned in the Constitution — made every effort to deliver holiday packages on time. During World War I, Army officers established a “Christmas box hospital” for the repair of Christmas boxes received in bad condition. And likewise, the Navy’s ships helped to ferry millions of packages from New York to Europe.

While technology has sped up the process, these packages still take time. Even in 2007, carriers still hand-sorted about 14 percent of letters and 40 percent of flat mail (larger pieces).

But that said, you still have a little time to send your last-minute gifts out. The U.S. Postal Service marks today as the deadline for priority mail with an expected delivery date of Dec. 25.

The General Post Office just before Christmas in London around 1930. (Imagno/Getty Images)

Postal workers with holiday gifts between 1910 and 1915. (Library of Congress)

First class mail pours down a chute on its way to the canceling machines at the General Post Office in New York City at Christmas. (Vecchio/Three Lions/Getty Images)

Christmas boxes for U.S. soldiers in December 1917. (Library of Congress)

An undated photo of a Christmas card vendor in New York. (Library of Congress)

A man sorts incoming Christmas mail in Corpus Christi, Tex., in December 1940. (Library of Congress)

A load of Christmas packages in December 1913. (Library of Congress)

Postal workers handle Christmas packages at the Main Post Office in D.C. in 1938. (Arthur Rothstein/Library of Congress)

People pack Christmas gifts for the U.S.S. Jason, which sailed from New York on Nov. 14, 1914, carrying about 6 million gifts for the children of Europe who were affected by World War I. (Library of Congress)

A Christmas post office “A la carte” in D.C. in 1921. (Library of Congress)

The year in photos, 2016