Which of the following did emma hart willard accomplish in 1826?

Emma Hart Willard  founded the first school for women's secondary and higher education in the United States -- the Troy Female Seminary in Troy, New York.

Emma Hart Willard (1787–1870) was born to a farming family in Connecticut. But her father, a farmer, encouraged his daughter to learn to read and write.  She went on to want to encourage education for other women.  The Troy Female Seminary, which she founded, actually was started in 1821 (not 1826) - I wonder if there's a typo in your question?  According to the National Park Service, Troy Female Seminary  is recognized as the country's first secondary school for females.  Emma Willard's goal was to provide young women with the same educational opportunites as men.

In 1895, The Troy Female Seminary was renamed The Emma Willard School in honor of the founder.  It operates today as a university-prep school / boarding school for young women in grades 9-12, with an enrollment in the 300s.