Though Catharine Maria Sedgwick (1789-1867) is frequently characterized as a regional author and best known for her novels set primarily in New England and New York City, she was, throughout the 19th-century, a popular author of periodical literature. Between 1825, with the appearance of “The Catholic Iroquois” in The Atlantic Souvenir and 1862, when she published her final work, “A Sketch from Life,” Sedgwick published nearly one-hundred sketches, tales, and works of short fiction in a wide range of periodicals, gift-books, and annuals. This paper seeks to provide a broad overview of these works focusing on the idea of border crossing. These texts record Sedgwick's actual travels across the US (including Niagara Falls, West Point, Saratoga Springs, and the Mississippi River) and abroad (including England, Italy, and Switzerland), which provide the basis for numerous published letters, sketches and stories. Sedgwick's innovative tales and sketches also cross generic boundaries wherein the lines between fiction and non-fiction frequently blur. Additionally, Sedgwick's periodical writings reflect her ongoing negotiation of 19th-century gender expectations as she and her characters navigate, cross, and reimagine the space between lady and writer, author and reader, wife and spinster, subject and citizen, American and cosmopolitan. Finally, this body of work reveals Sedgwick's ongoing interest in imaginative identifications, with stories that attempt to cross ethnic, racial, religious, and national borders (with varying degrees of success). My goal is to build on the understanding of Sedgwick as a transnational writer begun by other critics, including Melissa Homestead and Ellen Foster (eds. Clarence, Broadview Press 2012) and Lucinda Damon-Bach (Transatlantic Women: Nineteenth-Century American Women Writers and Great Britain, U of New Hampshire P, 2012), and to trace the development in her writing from regional to national to transnational and cosmopolitan views of literature, citizenship, and self.