The scores left both players among a tie for 28th, five shots behind co-leaders Azahara Munoz and Austin Ernst.
With world No. 1 Inbee Park not in the field this week in Virginia, Lewis can move up from No. 2 with a win or a solo second-place finish. Ko, who won last month and is currently No. 3 in the world, could grab the top spot with a win.
Lewis began with two birdies across her first three holes before setbacks at Nos. 6 and 9, adding a birdie on the par-5 15th to get back into red figures. Ko began her round on the 10th hole and opened with 10 straight pars before a lone bogey on the second hole, but the 17-year-old got the stroke back on the next hole and closed her round with a birdie on No. 9.
Other notable players near the lead after the first round include defending champ Cristie Kerr, a three-time winner at Kingsmill, and major winner Lexi Thompson, who both opened with rounds of 4-under 67. Former world No. 1 Yani Tseng also carded a 3-under 68 and sits three shots off the pace.