John Webster’s play The Duchess of Malfi is historically significant for a number of different reasons, including the following:

• It exemplifies the emergence of Webster as an important successor to Shakespeare as a writer of tragedies in the history of the English theater. Just as Shakespeare might be considered a kind of successor to Marlowe, so might Webster be seen as a kind of successor to Shakespeare.
• It exemplifies how relatively quickly the professional English theater had developed in a few short decades. Professional English theater (and theaters) hadn’t really existed before the final quarter of the sixteenth century.  By the time Webster wrote his play, however, theater (and theaters) in London had long since been well established.
• It exemplifies the darkening tone of English tragedy in the movement from the Elizabethan to the Jacobean periods. Jacobean tragedy is often considered sensationalistic when compared with earlier tragic works, and certainly this seems true of The Duchess of Malfi.
• It exemplifies the heavy influence of Italian literature, culture, and history on writings and writers of the English Renaissance. English writers were often fascinated by Italy, partly because by setting their plays in Italy they ran less risk of the censorship that might have resulted if they had dealt more often and openly with figures of recent English history.
• It exemplifies the heavy concern, in writings of the English Renaissance, with matters of morality and religion. Christian ideals – and the violation of those ideals – are very significant to the meaning of this play, and the same was true of much literature written during this period.
• It raises important issues about the place of women in Renaissance culture – issues that had especially come to prominence during the reign of Queen Elizabeth I.  How should a female ruler conduct herself, especially in matters of sexuality and marriage? What rights and responsibilities did she have?  These issues had been much discussed during Elizabeth’s reign, and they are obviously relevant to Webster’s play as well.
• It exemplifies the deep distrust that many people in early modern England felt for Roman Catholics and for Italy. Webster wrote during a time when Christendom was deeply divided between Catholics and Protestants, and the corrupt Catholics presented in Webster’s play would not have been surprising figures to many of his Protestant countrymen.
• It exemplifies the common concern at the time with issues of political virtue and vice, and especially with the proper function of a royal court.  This concern is evident, for example, when Antonio says that

. . . a prince’s court

Is like a common fountain, whence should flow

Pure silver drops in general, but if’t chance

Some cursed example poison ’t near the head,

Death and diseases through the whole land spread. (1.1.11-15)

Many of Webster’s contemporaries would have considered statements such as this relevant to conditions in England at the time.