Longest marathon on a seesaw (teeter totter)

According to Official Guinness Records,

The longest time spent continuously on a see-saw (teeter-totter) was 75 hr 10 min by Brandi Carbee and Natalie Svenvold at the Puyallup fair, Puyallup, Washington, USA from 11 to 14 September 2004.

For a complete list of 2004 records, please visit 2004 Guinness Records in United States.

Other United States records that might interest you:

• Largest collection of dice
• Heaviest limousine
• Longest scuba dive - open fresh water
• Most swords swallowed simultaneously by a female
• Heaviest turnip