My husband is related to the Leffler line through his mother's side of the family. Her great grandmother was a Rebecca Leffler born 1806 in Ohio, enroute to Fairfield County, OH from Washington Co., MD. Rebecca's parents were Peter (born abt 1772) and Catherine Leffler (maiden name unknown). When I first started reseaching this Leffler family, I kept coming up empty-handed and realized I would have to research all the early Leffler lines from PA, MD and OH between 1770-1810 to find any answers. I have accumulated quite a bit of information on various Leffler families, even some that isn't related.
I believe our Peter Leffler ancestor was a brother to Capt. Jacob Leffler (husband of Elizabeth Hewitt or possibly another wife, Catherine Miller (and also related to your George Leffler ancestor). Birth records for at least two of our Peter and Catherine Leffler's children were found in the St. Paul's Lutheran and German Reformed church near Clear Springs in Washington Co., MD and our Peter Leffler is found in the Conococheague Hundred District of Washington Co.(the same area) on the 1800 census.
If you look at a map of this area, it is very near the small village of Hyett, named after either Elizabeth Hewitt's father or at least a relative, who settled there. It's also near Hagerstown where some of Capt. Jacob and Elizabeth Leffler's children's birth records were found.
On that 1800 census, living nearby our Peter is also an elderly Jacob Leffler and an elderly female, whom I believe is Jacob Leffler Sr., the father of Capt. Jacob Leffler (Elizabeth Hewitt). By 1800, Capt. Jacob Leffler was already deceased and his wife, Elizabeth Hewitt Leffler remarried to Casper Simler. Their oldest son, Jacob Leffler (Jane Smith) is already accounted for on the 1800 census living in Donegal Twp., Washington Co., PA, along with his brother Isaac.