Merrill pursued a lifelong career as an educator, but she also served as a nurse during the
American Civil War. These two occupations were typical for unmarried women at that time and Merrill excelled at both. She also became a writer.
Educator Merrill began her teaching career at the private school her father founded in the family's home at Indianapolis, and assumed full responsibility for the school as he turned to other business pursuits. As the school's enrollment increased, it moved to the basement of the Fourth Presbyterian Church at Market and Delaware Streets. Later, it relocated to other sites in the city and became known as "Miss Merrill's School".
University professor In 1869,
Ovid Butler endowed the Demia Butler Chair of English Literature at North Western Christian University, now known as
Butler University, in honor of his daughter, a graduate of the university who had died in 1867. Butler endowed the chair, which still exists, on the condition that a woman would always retain the position. It was the first endowed chair at an American university designated for a female professor. Merrill accepted the appointment on April 21, 1869, and began teaching at Butler's campus on Indianapolis's near northside in the 1869–70 academic year. Merrill became the second female university professor in the country, preceded by
Maria Mitchell at
Vassar College the previous year. Merrill taught at Butler for fourteen years. According to the university's 2015–17 academic bulletin, Merrill was a pioneer in the use of new teaching methods, introducing the lecture method in her literature courses, a "first for any subject other than science." In 1875, when the university moved to a new site in the suburban community of
Irvington and changed its name to Butler, Merrill initially commuted to Irvington from her home in Indianapolis, but took up temporary residence in homes closer to the campus after the journey proved too time-consuming. Merrill, who loved the outdoors, enjoyed frequent walks in what became known as Irvington's Christian Park. She resigned from the professorship at Butler in 1883.
Writer Merrill became a writer, but it was not her main goal. Articles describing her travels in Europe from 1859 to 1861 regularly appeared in the
Indianapolis Journal and the
Lafayette Journal. Motivated by a sense of patriotic duty after the Civil War, Merrill wrote
The Soldier of Indiana in the War for the Union (2 volumes, 1866, 1869), a
history of Indiana soldiers' wartime experiences, at the request of Indiana governor
Oliver P. Morton. Because of Merrill's modesty, the work was published with no mention of her as its author. Merrill, who was not a trained historian, preferred to spotlight the sacrifices of the soldiers.
The Man Shakespeare and Other Essays (1902), a memorial collection of her written works, was published posthumously. Naturalist
John Muir, Merrill's longtime friend, wrote
Words from an Old Friend, which is included in the book, as a tribute to her.
Community servant Well known and respected in academia and in the city's social circles, Merrill was active in civic groups, delivered public lectures, and served on various committees. In 1867, Merrill and
Jane Chambers McKinney Graydon cofounded the Indianapolis Home for Friendless Women to aid women who were destitute, including penniless widows and former prostitutes. Merrill served on its board for many years. ==Later years==