Provided, That, as an express and fundamental condition to the acquisition of any territory from the Republic of Mexico by the United States, by virtue of any treaty which may be negotiated between them, and to the use by the Executive of the moneys herein appropriated, neither slavery nor involuntary servitude shall ever exist in any part of said territory, except for crime, whereof the party shall first be duly convicted. thumb|250px|Unrealized proposals to extend the Missouri Compromise line (originally defined in a way that limited it to the Louisiana Territory) all the way to the Pacific were advocated for by William W. Wick, James Polk, and Stephen Douglas, at various points. (Modern state boundaries are shown for reference. Iowa was not a state until December 1846 and Texas's border was not defined this way until 1850.) William W. Wick, Democrat of Indiana, attempted to eliminate total restriction of slavery by proposing an amendment that the Missouri Compromise line of latitude 36°30' simply be extended west to the Pacific. This was voted down 89–54. The vote to add the proviso to the bill was then called, and it passed by 83–64. A last-ditch effort by southerners to table the entire bill was defeated by 94–78, and then the entire bill was approved 85–80. These votes fell overwhelmingly along sectional rather than party lines.Morrison (1997), p. 41; Potter (1976), p. 22; Richards (2000), p. 152.
Provided, That, as an express and fundamental condition to the acquisition of any territory from the Republic of Mexico by the United States, by virtue of any treaty which may be negotiated between them, and to the use by the Executive of the moneys herein appropriated, neither slavery nor involuntary servitude shall ever exist in any part of said territory, except for crime, whereof the party shall first be duly convicted. thumb|250px|Unrealized proposals to extend the Missouri Compromise line (originally defined in a way that limited it to the Louisiana Territory) all the way to the Pacific were advocated for by William W. Wick, James Polk, and Stephen Douglas, at various points. (Modern state boundaries are shown for reference. Iowa was not a state until December 1846 and Texas's border was not defined this way until 1850.) William W. Wick, Democrat of Indiana, attempted to eliminate total restriction of slavery by proposing an amendment that the Missouri Compromise line of latitude 36°30' simply be extended west to the Pacific. This was voted down 89–54. The vote to add the proviso to the bill was then called, and it passed by 83–64. A last-ditch effort by southerners to table the entire bill was defeated by 94–78, and then the entire bill was approved 85–80. These votes fell overwhelmingly along sectional rather than party lines.Morrison (1997), p. 41; Potter (1976), p 22; Richards (2000), p. 152.