Describe the Underground Railroad in 5 COMPLETE SENTENCES or more.

The Underground Railroad was a network of secret routes and safe houses established in the United States during the early to mid-19th century, and used by enslaved African-Americans to escape into free states and Canada.[1] The scheme was assisted by abolitionists and others sympathetic to the cause of the escapees.[2] The enslaved who risked escape and those who aided them are also collectively referred to as the "Underground Railroad".[3] Various other routes led to Mexico,[4] where slavery had been abolished, or overseas.[5] An earlier escape route running south toward Florida, then a Spanish possession (except 1763–83), existed from the late 17th century until approximately 1790.[6][7] However, the network now generally known as the Underground Railroad was formed in the late 1700s. It ran north and grew steadily until the Civil War began.[8] One estimate suggests that, by 1850, 100,000 enslaved people had escaped via the network.[8]

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option d is correct. corroborated sources of historical evidence   is necessary to validate a claim about an event in history.

historians tend to use written sources, but audio and visual materials as well as artifacts are important objects that supply information to modern historians.

historical sources are usually divided into two categories: primary and secondary sources. depending on the historian's intent, some sources shift their designation. determining what type of sources toimplement, and the level of credibility and reliability of those sources, is a significant step in critical thinking for the historian.

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