From WHEAT LIFE:
"Flour sacks began replacing barrels as flour containers in the later 1800s, when the sewing machine made it possible to sew a sturdy sack that could hold flour. Flour sacks dominated the industry until the 1940s when paper sacks, which were introduced 20 years earlier, became the main form of packaging."
https://wheatlife.org/when-flour-was-sacked/
A lot of these old seed and flour sacks back in the day were manufactured by a Minneapolis company whose logo was a cat out of the bag! Ope!
(You need go no further than the Minnesota State Fair to see a superb permanent collection of seed and flour sacks right there in the Ag-Hort building, not far from the crop art.)