Q:

Was authorial intent ever taken seriously in academic literary theory?

What does the author mean? and What does the author want to say/convey/express/...? are questions we heard countless times during literature classes at school. In other words, it is a common didactic device. However, in the 1940s, W.K. Wimsatt and Monroe Beardsley, both representatives of the New Criticism, formulated their theory of the intentional fallacy, claiming that

the design or intention of the author is neither available nor desirable as a standard for judging the success of a work of literary art.

(See also the older question What is the “Intentional Fallacy”?.)
However, did older theories actually posit that the author's intention was the standard for interpreting and judging literature? Or have questions about authorial intent always been a teaching device that had little value in (academic) literary theory?

A:

Wimsatt and Beardsley's essay The Intentional Fallacy wasn't flogging a dead horse, nor did it bury the concept of authorial intent. 
One of the most influential statements of intentionalism is E. D. Hirsch's book Validity in Interpretation (1967). In an essay entitled "Why Intentionalism Won’t Go Away", Denis Dutton describes Hirsch's stance as follows (my emphasis):

Hirsch’s intentionalism stands apart from that of someone like Tolstoy because it is not so much a particular conception of art which motivates him to adopt it as it is a strongly held view of criticism. For Hirsch, unless we have a standard of interpretive correctness, criticism loses its status as a cognitive discipline. Without a notion of the author’s meaning as a guide — almost a regulative ideal, it would seem — criticism would be unable to decide between competing interpretations of works of literature (or art). The result, for Hirsch, would be chaos: anybody’s interpretation as good as anybody else’s. Hirsch does not deny, of course, that works of art may mean different things to critics or to audiences in different historical epochs. This is in fact how it is that works of art can have different significances to people. But the meaning of a text is always one and the same thing: it is a meaning that the work had for its maker, the artist or writer.

Hirsch's brand of intentionalism isn't the only one; there is also a weaker form known as hypothetical intentionalism. One representative of this type of intentionalism, Alexander Nehamas, argues that

interpretation is a matter of attributing an intended meaning to a hypothetical author, distinct from the historical writer. This view allows the interpreter to find meaning even in features of the work that may have been mere accidents on the part of the historical writer.

(Quoted from Teaching and Learning Guide for: Authors, Intentions and Literary Meaning by Sherri Irvin.)
In summary, one can say that intentionalism is not dead but is the subject of theoretical debate.

