Elizabeth Barrett Browning wrote to the American author, James Russell Lowell, about her "Slave-poem" on 17 December 1846. Lowell, and other American poets of his generation, have the distinction of being the first generation of American poets who were as famous as their British counterparts. Lowell has been described as ". . . a vital force in the history of American literature and throughout his lifetime." (The Poetry Foundation's biography of Lowell, https://www.poetryfoundation.org/poems-and-poets/poets/detail/james-russell-lowell). This letter, though brief, shows the high regard in which Lowell was held by Elizabeth Barrett Browning.
This letter, and others between Robert and Elizabeth Browning and James Russell Lowell can be found in the Armstrong Browning Library, and online in Baylor's collection of The Browning Letters.
The Armstrong Browning Library holds many anti-slavery works and held an exhibit of these items in 2015. They also wrote a blog post about the exhibit, which you can read.
The musical The King and I takes place in Thailand not long after the publication of Harriet Beecher Stowe's book Uncle Tom's Cabin. Anna, tutor to the King of Siam's children, has read and greatly admires the book and, transformed for a Thai culture, the core of the book becomes part of a royal entertainment for the King. The section "Small House of Uncle Tom" from a 2012 production is below if you would like to see one of the ways that the story spread the anti-slavery message in its own time.
From the BCA AVPA Theater Department production of March 2 & 3, 2012 in Hackensack, NJ. Over 200 students from all Academies participated. Directed by Victoria Pero, produced by Rebecca Strum, choreographed by Laurie Crochet after the original work of Jerome Robbins. Vocal direction by Patrick Finley, musical instrumental direction by Michael Lemma.