Taffy Brower, Carolyn Creekmore and Robin Donnelley share second place at 5-over-par 77 at Pasatiempo Golf Club. Patricia Cornett, Debbie Franco and Martha Lang are one stroke further back at plus-6.
Butler, who reached the semifinals of the 2002 Senior Women's Amateur, managed three birdies on her round. The 2002 Senior Women's Amateur was her first USGA event since playing in a U.S. Girls' Junior as a teenager.
'Before the day started, I would have taken it in a heartbeat,' said Butler of her opening 76. 'I'm not surprised because I know what I can do, but I don't play many tournaments and have trouble taking my game into competition.'
Elizabeth Haines posted a 7-over-par 79. She shares eighth place with Rose Pagan, Karen Ferree and Patty Crigler.
Carol Semple Thompson, a four-time winner of this event, carded an 8-over-par 80. She is tied there by Marcia Fisher, Claudeen Lindberg, Toni Wiesner, Marian Barker and Reggie Parker.
Marlene Streit, who became the oldest USGA champion at 69-years-old when she won this event last year, carded a 14-over-par 86 and is tied for 51st.
At the conclusion the two stroke-play rounds, the field will be cut to 64 players who will move on to the match play portion of the event.
The first round of match play will take play on Monday, with the second and third rounds scheduled for Tuesday. The quarterfinals and semifinals are slated for Wednesday with the 18-hole final to be played on Thursday.