US teen Lexi Thompson, trying to become the youngest winner in the LPGA's 61-year history, fired a five-under par 67 to seize a five-stroke lead at the Navistar Classic. Prodigy Thompson, who turned 16 last February, finished 54 holes on 15-under par 201 at the $1.3 million event and was poised to shatter LPGA age marks and collect her first elite-level victory. "I always go into every tournament wanting to win," Thompson said. "I'm at 15, so my goal is to take it one shot at a time and try to get it to 20." American Marlene Hagge captured the 18-hole Sarasota Open in 1952 just two weeks past her 18th birthday to become the LPGA's youngest winner. American Paula Creamer was nine months and 17 days past her 18th birthday when she won the 2005 Sybase Classic, becoming the youngest winner of a typical multi-round event. South Korean Meena Lee was second on 206 with England's Karen Stupples, Becky Morgan of Wales and American Tiffany Joh sharing third on 208, seven adrift of Thompson's pace. It's the second time this season that Thompson, not yet an LPGA member, has challenged for a record-smashing title. "It's incredible," said Juli Inkster, a Hall of Famer with 31 career victories who said she started playing when she was 15. "They're just starting younger and they're just so much better." Thompson led after 54 holes at an LPGA event in Mobile, Alabama, earlier this year but a final-round collapse on May 1 left her in a share of 19th. But on Saturday, Thompson, clad in pink with her blonde hair tied into a ponytail by a pink bow, dominated under perfect conditions on the Robert Trent Jones Trail course. Thompson, whose father Scott serves as her caddie, birdied the par-4 fourth, then ran off four birdies in a row to finish the front nine, giving her a five-stroke lead. Another birdie at the par-4 15th stretched the lead to six. Thompson gave back another stroke to par with a bogey at 18 but playing partners Morgan and Stacy Lewis of the United States made bogeys as well. Winning would not automatically make Thompson a member of the elite circuit. Thompson has successfully petitioned for a place in this year's LPGA qualifying tournament. A victory Sunday would allow her to seek LPGA membership but because of her youth the move would have to be approved by tour officials.