There are 28 dance cards scattered throughout Mr. Boller's scrapbook.
Nearly every resources discussing the history of dance cards indicates that dance cards are small booklets used by women at formal dances in the nineteenth and early twentieth centuries. Evidenced by Mr. Boller’s collection, though, dance cards were used by men as well. It only makes sense that all party-goers, regardless of gender, would need to keep track of whom they promised to dance with next.
When examining Mr. Boller’s collection of dance cards one will observe that a few have long strings hanging from them and all have a small hole punctured through them where strings would have been. The strings were there so women could wear the card on their wrists. Inside the card there is a lists of the order of the dances. It also indicates the type of dance; waltz, polka, quadrille, lancers, bon ton, esmeralda, gallop, Newport, Parissienne, prairie queen, schottische, etc. Next to each dance there is a blank line to write the name of one’s dance partner for that particular dance.
Some of the cards are quite pretty with beautiful images on the front. Mostly, though, they provide historical information about Mr. Boller’s social calendar; dates of the event, location, sponsors, popular dances of the time, and who he danced with! In some instances we see Mr. Boller involved in the planning of dances specifically for the company he worked for; Montgomery Ward & Co.
Dance cards lost their popularity before the middle of the twentieth century due to less rigid gender and etiquette practices but one can still hear phrases today that are derived from these ephemeral objects such as "Pencil me in" and "Save the last dance for me." 
 "Exhibitions: 'From the Waltz to the Jitterbug': Dances at Syracuse University, 1900 -1660: What is a Dance Card?" Syracuse University Archives. Accessed Wednesday, October 21, 2015.http://archives.syr.edu/exhibits/dances_card.html.
 "Exhibitions: 'From the Waltz to the Jitterbug.'"
To Learn More About American Ballroom Dancing during the early 1900s:
Library of Congress, American Balroom Companion: https://memory.loc.gov/ammem/dihtml/ [Note: Once there, click on "Video Directory" to see demonstrations of the dances Mr. Boller would have engaged at at any one of the many balls he attended.]