House Rule 21, also known as the Gag Rule, prohibited abolition petitions from being read on the floor of the House, passed on January 28th 1840.
The House of Representatives adopted a series of rules between 1836 and 1844 banning petitions for the abolition of slavery. Known as the gag rules, they prevented antislavery petitions from having to be read according to usual House procedures. House rules had been that during the first thirty days of each session of Congress was for reading of petitions from the people. Each petition would be read aloud, printed and assigned to committee. Slave owning southern Representatives had no attentions of abolishing slavery and were incensed by the antislavery petitions.
The House of Representatives passed the 21st Rule; January 27th 1840, it banned even the acceptance of antislavery petitions. The Rule passed by the slim vote of 114 to 108, being opposed by Northern Democrats and Whigs. The Rule would stand until December 3rd 1844 when all the Northern Whigs, along with three quarters of the Northern Democrats and four Southern Whigs voted to repeal the Gag Rule.