Why did the American guards yell “Ladies first!” and push the men away from the water pail?

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In Marie Priesland's memoir, why did the American guards yell “Ladies first!” and push the men away from the water pail?

In the recollection of her arrival to the United States, Priesland describes a warm day, and everyone being thirsty. The guards brought a pail of water and, as soon as men attempted to drink, insisted on women drinking first because it´s an American custom.

Explanation:

This was shocking for the Slovenian women because in their country "women were always second to men."

b)

it created free trade throughout the colonial territories.