well into the nineteenth century, the diet in the United States was mostly meat, very little in the way of vegetables, no refined sugar, and very little in the way of refined grains, either. The “diseases of Western civilization” were not nearly as prevalent as they are now, and children grew to be fine strapping adults, taller and healthier than people from almost every other country
Have you ever gone to visit old houses from the 18th century? The ceiling heights were pretty low. The average height has increased since then
This article mentions that and explains:
In fact, over the last 150 years the average height of people in industrialized nations has increased approximately 10 centimeters
the observed increase in height has not been continuous since the dawn of man; it began sometime around the middle of the nineteenth century. In fact, examinations of skeletons show no significant differences in height from the stone age through the early 1800s. Also, during World Wars I and II, when hunger was a frequent companion of the German civilian population, the heights of the children actually declined. They only recovered during the post-war years.
Such data are consistent with recent research indicating that slow growth induced by temporary malnourishment can usually be reversed. Chronic underfeeding during childhood, however, permanently affects stature and other traits, including intelligence
https://www.scientificamerican.com/article/why-are-we-getting-taller/