Nationalism required personalizing a nation. Countries were often portrayed as female to give shape to an abstract idea. Often cultural icons such as trees or aspirational values such as liberty and justice needed icons and preferably female figures to get the message across. The female figure became an allegory of the nation.
For example, under French Revolution, justice is generally a blindfolded woman carrying a pair of weighing scales. Later, in France Marianne emerged as the representation of France. Her features were also drawn from the symbol of liberty and the republic. She wore a red cap with the tricolour cockade.