Complex sentence: September 17 2008 marked the 17th year the Pledge Across America takes place, and it also marked 117 years since Francis Bellamy wrote and first recited the Pledge of Allegiance in 1892.
Split into simpler sentences: September 17 2008 will mark the 17th year the Pledge Across America takes place. And 117 years since Frances Belemy wrote and first recited the Pledge of Allegiance in 1892.