Millay reached maturity during a traumatic period of world history. In 1918, War and a Flu Pandemic coincided, killing swaths of young people. Written at least two years later, “Spring” reflects how heavily Americans remained in mourning after these events.

World War I began in 1914 after the assassination of Archduke Franz Ferdinand, heir to the Austro-Hungarian Empire. Due to a complex network of alliances and rivalries, War broke out across Europe. The United States entered the War in 1917, a year before the conflict officially ended.

The War became remembered for its brutality, thanks to innovations in warfare. Mustard gas, infamously, burned and suffocated soldiers in trenches. The War killed 8,528,831 and wounded 21,189,154 combatants by its end. 116,516 Americans died.

Because military personnel traveled across the sea and countryside, their movements aided in spreading a new strain of influenza. The strain then called the Spanish Influenza evolved into the Pandemic of 1918. The 1918 Pandemic lasted until 1919, though the virus remained seasonally active.

Unlike previous strains, the 1918 strain hit healthy young people the hardest. The United States Center for Disease Control reported that the deceased flu patients' average age was 28. Once people contracted the virus, they quickly became violently ill, with some dying reportedly within a day.