McPherson, Teresa Lu and Katherine Hull were all a stroke ahead of Sherri Turner. Those four were among the few who finished the first round by the early evening. Heavy rain fell during the morning at Pinnacle Country Club, delaying the start of the 54-hole event by 4 1/2 hours.
'Really lucky to get 18 holes in,' McPherson said. 'We woke up this morning and came out here on four different occasions.'
U.S. Women's Open champion Cristie Kerr was in contention after a 69, but several of the tournament's top draws started so late they had little hope of finishing. Natalie Gulbis, for example, started around 4:40 p.m.
McPherson, who played college golf at South Carolina, turned pro in 2003. She played on the Futures Tour until she finished high enough on that money list to earn her LPGA Tour card for 2007. Her highest finish this year is a tie for 18th in July at the Jamie Farr Owens Corning Classic.
She could have had sole possession of the lead, but missed a short par putt on No. 17.
Lu said the rain softened the 6,238-yard course. Even after play finally started, players had to contend with an occasional drizzle.
'The fairways are pretty wet and the greens are holding pretty good because it's wet,' she said. 'The green speed is pretty good.'
Several early finishers joined Kerr at 3 under, including Dorothy Delasin, Alena Sharp, Pat Hurst and Julieta Granada.
The top three money earners this year on the LPGA Tour -- Lorena Ochoa, Suzann Pettersen and Paula Creamer -- are absent from this event, and No. 4 Mi Hyun Kim withdrew.
This is the LPGA's first visit to Arkansas since the Arkansas Open at Hot Springs in 1956.