Elder Orson F. Whitney seemed destined to serve in LDS Church leadership as he was a grandson of early church leaders Heber C. Kimball and Newel K. Whitney. As a young man of 22 years, Elder Whitney was called on a mission to proclaim the tenets of the LDS Church among the population of Pennsylvania. During his missionary labors, he had a dream where he witnessed the suffering in Gethsemane and crucifixion of Jesus Christ. This dream had a powerful effect on the young man. His discipleship was made sure at this time and he led a life of service to the Church and his fellow man.
As always, a wealth of information can be found at Grandpa Bill's G. A. Pages here.
You can find the monument with this map.
Thanks to my friend Mike S., for helping me originally locating his marker. Mike is a relative of Elder Whitney.