A two-hour fog delay during the morning left the 132-man field without enough daylight to complete the first round and there were still 49 players on the Seaside Course at the Sea Island Resort when play was halted.
McNeill ran off five straight birdies in the midst of his round while opening a bid to win for the third time on the PGA Tour.
He had a one-shot lead over Brian Gay and Briny Baird, both of whom shot a 7-under 63 during the morning. Gay is still trying to recover from the affects of traveling from China to Georgia after last week's World Golf Championship event in Shanghai.
Baird is seeking his first tour event in 365 starts. He is back in action after undergoing surgery on both shoulders.
Webb Simpson, already a winner in the 2014 campaign with a triumph at the Shriners Hospitals for Children Open, finished with a 5-under 65. Kevin Kisner, Seung-Yul Noh and Kevin Chappell were also at 65 while Robert Garrigus stood at 5-under with five holes to play.