Cohlmia didn't have a bogey in his round and holds a one-stroke advantage on J.C. Horne of Daytona Beach, Fla. and Ben Fox of Studio City, Calif. going into Tuesday's play at Gold Mountain Golf Club's Olympic Course.
'My putter was pretty spectacular,' said Cohlmia, who is playing in his first USGA event and will be a senior at the University of Tulsa in this fall.
Martin Ureta, the 2005 APL runner-up, and Justin Metzger both shot 3-under-par 69s.
Derek Fathauer, John Cassidy, Lindsay Renolds, Scotty Jones and Tyler Trout are all three strokes off the pace.
Defending champion Clay Ogden of West Point, Utah, shot a 1-over-par 73.
One of the oldest United States Golf Association events, the U.S. Amateur Public Links Championship is being held for the 81st time. Some of the past winners who have gone on to have professional careers are: Jodie Mudd, Billy Mayfair, Trevor Immelman, David Berganio, Jr. and 2004 champion Ryan Moore.
Immelman picked up his first PGA Tour win this past weekend at the Western Open, beating Tiger Woods and Mathew Goggin by two shots.
The second round of stroke play will be played Tuesday before the field is cut to the low 64 scorers. The first round of match play will be Wednesday and the championship runs through Saturday's 36-hole final.