Ercildoun, population about 100, is an unincorporated community in East Fallowfield Township, Chester County, Pennsylvania, United States.

[3] The name "Ercildoun" was taken from the poem, "Thomas the Rhymer" by Sir Walter Scott when the hamlet's post office opened in 1850, but it was misspelled "Ercildown" until 1854.

In 1811 the current Fallowfields Friends Meeting House was built, which, with the adjoining cemetery, People's Hall, and the former post office - now a grocery store, forms the center of town.

Arising from Quaker beliefs, the abolitionist East Fallowfield Anti-Slavery Society was formed in 1835 with James Fulton Jr. as the recording secretary, and 33 other members.

[2] In its first annual report the Society stated that they had distributed 3,000 books and tracts and gathered signatures petitioning Congress to abolish slavery in the District of Columbia and the territories.

[5] The Anti-Slavery Society met in the Fallowfield Meetinghouse until the winter of 1844, when Abby Kelley and Charles Burleigh spoke at a meeting that was broken up by a mob of anti-abolitionists.

Ercildoun's location about 15 miles north of the slave state of Maryland contributed to this activity, and the hamlet fed both the northern and southern Pennsylvania branches of the Underground Railroad both before and during the Civil War.