The division was mustered into service for the Spanish–American War in 1898. Pennsylvania was initially levied 10,800 men, in ten infantry regiments and four artillery batteries. The entire division was mustered into service between 6 May and 22 July, and while 8,900 men had assembled at Mount Gretna for the muster parade on 28 April 1898, there was no difficulty in raising 12,000 men for service in two and a half months. However, only the 4th, 10th, and 16th Regiments, three artillery batteries, and three cavalry troops were deployed, to Puerto Rico. The 10th Regiment was then sent to the Philippines, being ordered home on 30 June 1899.