From Wiki:
http://en.wikipedia.org/wiki/Civil_Rights_Act_of_1964The prohibition on sex discrimination was added by Howard W. Smith, a powerful Virginian Democrat who chaired the House Rules Committee and who had strongly opposed the Civil Rights Act. The addition of "sex" to title VII is commonly described as a cynical attempt to defeat the bill by inserting objectionable amendments.<10><11><12> Smith knew Republicans, who had included equal rights for women in their party's platform since 1944, would vote for the amendment along with southern Democrats and get it in the final bill.<12> Smith thought that northern Democrats would not vote for the bill due to the inclusion of gender, because the clause was opposed by labor unions which the northern Democrats aligned themselves with.<12> Representative Carl Elliott of Alabama later claimed, "Smith didn't give a damn about women's rights...he was trying to knock off votes either then or down the line because there was always a hard core of men who didn't favor women's rights,"<13> and the Congressional Record records that Smith was greeted by laughter when he introduced the amendment.<14>
Smith nevertheless claimed that he sincerely supported the amendment and made serious arguments in its favor.<14> The claim was not entirely ungrounded, as Smith had long been close to Alice Paul, a women's rights activist who urged him to include sex as a protected category. The amendment had been forcefully promoted by the National Woman's Party and its allies in Congress, who had no desire to scuttle the Civil Rights Act.<10> Thus, as William Rehnquist explained in Meritor Savings Bank v. Vinson, “The prohibition against discrimination based on sex was added to Title VII at the last minute on the floor of the House of Representatives...the bill quickly passed as amended, and we are left with little legislative history to guide us in interpreting the Act’s prohibition against discrimination based on ‘sex.’” <15>