CARMEL, Ind. -- Here is where the leaderboard stands after 18 holes:
• Recent First-Round Leaders in the U.S. Senior Open Championship:
• One of the day's best showings was turned in by 50-year-old Jackson, an amateur competitor from Germantown, TN, who shot a 6-under-par 66 and is tied for the lead. Jackson's 66 established a new record for the low round by an amateur in this event. The previous low was 68 by four players, most recently by Rick Cloninger last year in Colorado. A two-time winner of the U.S. Mid-Amateur Championship (1994, 2001), Jackson was also a member of two United States Walker Cup squads (1995, 1999). He finished strong, carding a 5-under-par 31 over his final nine.
• Norman and Bean were the only two players in the field to get to 7-under-par during their rounds but neither could remain there. Norman was at 7-under-par with one hole remaining but bogeyed No. 18 to drop back into a tie for the lead. Bean reached 7-under with three holes remaining but made bogeys at Nos. 7 and 9 to finish at 5-under-par 67.
• Less than a week after winning his second Senior British Open title, Loren Roberts got off to a good start, firing a 4-under-par 68. He is currently T7. Also T7 is 2007 U.S. Senior Open winner Brad Bryant. Like co-leader Jackson, Roberts resides in Germantown, TN.
• Defending champion Eduardo Romero began defense of his title with a 1-over-par 73 and is currently T52.
• Competitors are playing the longest course in U.S. Senior Open history at 7,316 yards. The previous longest was at The Broadmoor Golf Club last year at 7,254 yards.
• A number of players are competing in their third consecutive major championship. Tom Watson, Bruce Vaughan, Norman, Tom Lehman and Mark O'Meara all played the British Open and the Senior British Open Championships prior to coming to this year's U.S. Senior Open. Watson is currently T26, O'Meara T16, Vaughan T6, Norman T1 and Lehman T7
• Only two international players are among the top 25 players on the leaderboard -- (T1/Australia) and Allem (T5/South Africa).
• Hole No. 16 was the most difficult with an average score of 4.448 (+.448), while No. 11 was the easiest at 4.762 (-.238).