In the middle of the nineteenth century, most of the British people started to live in large cities thanks to Industrial Revolution, but this situation brought some down-sides into the daily life of citizens such as poverty, violence and totally freedom in sex. These things became the usual parts of daily life after a while. Most of the popular writers of that period chose to use these down-sides in their writings in order to affect their readers more and more.
Robert Browning, who wrote "My Last Duchess" in 1842, was one of the authors who used these down-sides of city life in their writings.
"My Last Duchess" is written down in first person narrator male protagonist point of view. The speaker in the poem is most likely Alfonso II d'Este, the fifth Duke of Ferrera, who is noble with his surname too much as it mentioned in the poem at the 33th stanza with "[m]y gift of a nine-hundred-years-old name" (Browning), can't handle with her wife's warm nature and kills her. This cruel habit of the Duke and the warm nature of the wife in this poem have lots of symbolic meanings as reflections of the down-sides of the city life that I mentioned above.
First of all, how women are cruelly domesticated by the hegemony of masculinity is one of the major themes of "My Last Duchess". Even just being kind, polite and thankful person is totally wrong thing as a woman who lives in that era. Professor Clinton Machann says in the "Browning's Chivalrous Christianity" section of his book "Masculinity in Four Victorian Epics: A Darwinist Reading" that,
Third, apart from Browning's relationship with his wife, an emphasis on gender and - of special interest here- complex themes related to masculinity, are central to his work as a whole. ... Browning probably modeled this classic portrait of an aristocratic male domestic tyrant on Alfonso II, fifth and last duke of Ferrara (1553-97), whose young bride Lucrezia died under mysterious circumstances in 1561" (Ma...