Commentary Past installments in the “Understanding the Constitution” series have focused mostly on the original, un-amended document. This two-part essay is a primer on the longest amendment ever adopted—the 14th. Some say it’s the most important amendment, because it empowered the federal government to protect people from state government abuse. Even before the Civil War was over, Congress proposed the 13th Amendment, abolishing slavery. By the end of 1865, the requisite three-fourths of the states had ratified it. However, the Republicans then controlling Congress favored an additional amendment to protect former slaves from maltreatment in the Southern states and to prevent a later Democratic Congress from repudiating Union war debts or paying Confederate debts. More critically, Republicans needed an amendment to validate their Civil Rights Act, passed over President Andrew Johnson’s veto on April 9, 1866, but then of dubious constitutionality. On June 13, 1866, Congress formally proposed the 14th …