How has the definition of work changed by 1900?

The definition of work changed by the 1900s because America went through an industrial revolution. It completely changed society and also changed the concept of work.

Before America was mostly a rural country and people were used to work on farms and they used to live in small cities. With industrialization, people started to move to big cities, where the industries were located. Work became restricted to industries, people had terrible workplaces, they endured long journeys of 12 hours per day of work.

your list doesn't mention any of them at all.

and what does "these" mean anyway ?

pepin the short[a] (german: pippin der kurze, french: pépin le bref, c. 714 – 24 september 768) was the king of the franks from 751 until his death. he was the first of the carolingians to become king.[b][2]

the younger son of the frankish prince charles martel and his wife rotrude, pepin's upbringing was distinguished by the ecclesiastical education he had received from the monks of st. denis. succeeding his father as the mayor of the palace in 741, pepin reigned over francia jointly with his elder brother carloman. pepin ruled in neustria, burgundy, and provence, while his brother carloman established himself in austrasia, alemannia and thuringia. the brothers were active in suppressing revolts led by the bavarians, aquitanians, saxons, and the alemanni in the early years of their reign. in 743, they ended the frankish interregnum by choosing childeric iii, who was to be the last merovingian monarch, as figurehead king of the franks.