Question: Where did these two phrases come from? Why *stairway* and *highway*?

My own research didn't turn up results on Google that traced the origins of the phrases. I can only speculate (as stated in the comments) that the "stairway to heaven" phrase may derive from Jacob's ladder in Genesis 28 of the Bible, and that "highway to hell" may have just meant "the main road to hell" more than a century ago. [Wikipedia](https://en.wikipedia.org/wiki/Highway) says that *highway* once may have meant "the main road", as modern highway systems, that differ from ancient roads, are 20th century constructions; and I can find the phrase "[highway to hell](https://books.google.com/books?id=WBfLozOs_34C&pg=RA1-PA10&dq=highway+to+hell&hl=en&sa=X&ved=2ahUKEwjQtP-r6PXvAhXWwQIHHZXZAywQ6AEwAnoECAIQAg#v=onepage&q=highway%20to%20hell&f=false)" as far back as the 1600s.

Answer: 
The Bible.

"Stairway to heaven" is a reference to what is also often referred to as "Jacob's ladder," a ladder the prophet Jacob saw in a dream leading to heaven. In Latin, the original language the Bible was compiled in, the word for "ladder" (i.e., "scalam") is the same word as the word for "stairway" (i.e., "scalam"), which is why what gets called a "ladder" in the King James Version (KJV) of the Bible, for example, is called a "stairway" in other translations, like the New International Version (NIV) and New Living Translation (NLT):

> 
> "As he slept, he dreamed of a **stairway** that reached from the earth up
> **to heaven**. And he saw the angels of God going up and down the
> stairway." -Genesis 28:12
> 
> 
> 

Likewise, "highway to hell" is a reference to what is also referred to as the "road to destruction" by Jesus in the KJV of the Bible, like in the NLT:

> 
> "You can enter God’s Kingdom only through the narrow gate. The **highway
> to hell** is broad, and its gate is wide for the many who choose that
> way." -Matthew 7:13
> 
> 
> 

Both phrases, "stairway to heaven" and "highway to hell," originated from the Bible through these two extremely famous passages by way of various translations, not just various Protestant translations as a consequence of the Reformation in the 16th century but also in the English vernacular even before then by way of Catholic priests in general translating and interpreting the Bible, which was theretofore written only in Latin, into English for sermons to parishioners and in their day-to-day discussions with parishioners and others, English-speaking laypeople who didn't speak Latin and whom Catholic priests were indoctrinating with their various English translations and interpretations of Bible stories and passages written only in Latin.

Therefore, the Biblical origin of these two English phrases, "stairway to heaven" and "highway to hell," goes back well before the rock bands Led Zeppelin and AC/DC sang them in the 1970s, from Modern English through Middle English even back to Old English, so going back more than a thousand years and first coming into English via Catholic priests fluent in English and Latin reading and interpreting and/or translating into English from *Biblia Sacra Vulgata* (i.e., the *Vulgate*), the original, late-4th-century, Latin compilation of the Bible, which has been in continuous use since the late 4th century and continues to be used to this day by the Roman Catholic Church as its canon.
I think the OP is already close to getting the answer already?
It has to do with the anticipated numbers of people going to each place.

Matthew 7:13
(New Living Translation)

> 
> “You can enter God’s Kingdom only through the narrow gate. The highway
> to hell is broad, and its gate is wide for the many who choose that
> way."
> 
> 
>