Question: What American holiday was campaigned for by author, Sarah Josepha Hale, whose work was published in an American periodical in the 19th Century?

Context paragraphs:
Arthur's Magazine: Arthur's Magazine (1844–1846) was an American literary periodical published in Philadelphia in the 19th century.  Edited by T.S. Arthur, it featured work by Edgar A. Poe, J.H. Ingraham, Sarah Josepha Hale, Thomas G. Spear, and others.  In May 1846 it was merged into "Godey's Lady's Book".

Christian Examiner: The Christian Examiner was an American periodical published in the 19th century.

William Llewellyn Wilson: William Llewellyn Wilson was a Baltimore-born African American conductor, musician and music educator.  He was the first conductor of the first African American symphony in the city of Baltimore.  A notable cellist, Wilson was also a music critic for the "Afro-American", a major African American periodical in Baltimore in the early 20th century.

Liberia; or, Mr. Peyton's Experiments: Liberia; or, Mr. Peyton's Experiments is an 1853 novel by Sarah Josepha Hale, the author of the nursery rhyme "Mary Had a Little Lamb", who wrote the novel under the name of Sara J. Hale.

Sarah Josepha Hale: Sarah Josepha Buell Hale (October 24, 1788 – April 30, 1879) was an American writer and an influential editor.  She is the author of the nursery rhyme "Mary Had a Little Lamb".  Hale famously campaigned for the creation of the American holiday known as Thanksgiving, and for the completion of the Bunker Hill Monument.

Truth Seeker: Truth Seeker is an American periodical published beginning during the 19th century.  It was considered the most influential Freethought publication during the period following the Civil War into the first decades of the 20th Century, known as the Golden Age of Freethought.  Though there were other influential Freethought periodicals, "Truth Seeker" was the only one with a national circulation.  The headquarters is in San Diego, California.

Luisa Battistati: Luisa Battistati was an Italian 19th century woman who is recorded in American writer Sarah Josepha Hale’s "Sketches of all distinguished women" (1853) as a heroine of the insurrection against Austrian rule that had taken place in Lombardy known as the Five Days of Milan.  The revolt took place during the period 18–22 March 1848 and was successful in expelling the Austrian garrison, commanded by Josef Radetzky, from the city.  Radetzky would re-enter Milan on 6 August of that year, however, and Austria remained in control of the city until 1859.

Alfred Hoffy: Alfred A. Hoffy (1796–1872) was a mid 19th century American lithographer and botanical illustrator who founded the first American periodical devoted solely to fruit cultivation.

Boston Seaman's Aid Society: The Seaman’s Aid Society of the City of Boston was a women's aid charity founded in Boston in 1833 with the goal of improving the condition and character of seamen and their families.  The first president of the society was famed author, poet, and editor Sarah Josepha Hale.  Affiliated with the Boston Port Society, the women of the Seaman's Aid Society operated a clothing store; the Mariners House, a boarding house for seamen; and a free school for mariners' daughters in Boston's North Square.  In 1867, the society merged with the Boston Port Society to form the Boston Port and Seamen's Aid Society.

Soccer America College Team of the Century: The "Soccer America" College Team of the Century were chosen by the editors of the American periodical "Soccer America" to comprise, as one men's and one women's eleven-member side divided each as one goalkeeper, three defenders, four midfielders, and three forwards, the best players of collegiate association football in the United States of the 20th century CE.

Supporting paragraphs: Arthur's Magazine Sarah Josepha Hale
Answer: Thanksgiving