Size does matter....eat meat!!
height is genreally related to two major factors:
1. High protein intake. It is possible that at the time, hunting was still used to obtain food and this would generally result in a larger individual.
2. Lack of chronic disease is the most important factor. IT appears that the people of that age were fairly healthy. This was probably due to a lack of large population centers that would be the centers of disease.
Men in the the 1790s were as tall as those of WWII, according to Army records. Between those times we got smaller as our cities developed due to the influx of immigrants.
A Good discussion of this is in the "The Fourth Great Awakening".