There are some Biblical allusions in the idea of the “King's Highway”.
“In those days John the Baptist appeared in the wilderness of Judea, proclaiming, “Repent, for the kingdom of heaven has come near.” This is the one of whom the prophet Isaiah spoke when he said, “The voice of one crying out in the wilderness: ‘Prepare the way of the Lord, make his paths straight.’”” (Matthew 3:1–3 NRSV)
“He [John] went into all the region around the Jordan, proclaiming a baptism of repentance for the forgiveness of sins, as it is written in the book of the words of the prophet Isaiah, “The voice of one crying out in the wilderness: ‘Prepare the way of the Lord, make his paths straight.” (Luke 3:3–4 NRSV)
These texts (and another one in Mark) are quoting from Isaiah.
“Comfort, O comfort my people, says your God. Speak tenderly to Jerusalem, and cry to her that she has served her term, that her penalty is paid, that she has received from the LORD’S hand double for all her sins. A voice cries out: “In the wilderness prepare the way of the LORD, make straight in the desert a highway for our God. Every valley shall be lifted up, and every mountain and hill be made low; the uneven ground shall become level, and the rough places a plain. Then the glory of the LORD shall be revealed, and all people shall see it together, for the mouth of the LORD has spoken.”” (Isaiah 40:1–5 NRSV)
Undoubtedly, when she wrote about the King's Highway, Ellen White had in mind the Isaiah text used in connection with John the Baptist's call for repentance. Is it possible that we are delaying the King because we are not clearing His Highway?
Ellen White might also have been familiar with some stories or poems that talk about the King's Highway.
The Hidden Reward
Annie A. Preston
A German duke, of great renown,
Who dwelt quite near a famous town
Clothed like a beggar, placed one day
A large stone in the king’s highway.
’T was near his grand old palace gate,
And there he sat him down to wait.
Soon came that way young peasant Bart,
With oxen strong and lumbering cart,
“This rock will not get moved by me.
This is the duke’s affair,” cried he.
Next a gay soldier marched along,
With cockade hat and merry song;
Too high he looked the stone to see,
Se fell, of course, and cried, “Ah, me!
Misfortune take the blockheads all
Who caused like this a brave man’s fall!”
Soon merchants came, bound for the fair,
With horses find and offerings rare;
To ‘scape the stone they filed each side
(The loads were broad, the road not wide),
“How long,” they jeered, “will that rock stay,
And thus impede the duke’s highway?”
The duke sent out his writ of state
For all to gather at the gate.
The place was thronged on either side
By rich and poor from far and wide.
Then in the road in rich array
Appeared the duke, and thus did say:
“This rock, good friends, was placed by me,
That I your shiftlessness might see.”
With his own hands aside he rolled
The stone, and showed a pot of gold
That lay beneath, a precious gift
For him who should the stone uplift.”
Published in Golden hours: A Magazine for Boys and Girls (1878)
There is also a story about “The King's Highway” by an unknown author that can be found on several different web sites. I don't know how old the story is so I can't say if Ellen White possibly could have known about it. But it does help illustrate the concept of clearing the King's Highway.
Once upon a time a king had a great highway built for the people of his kingdom. After it was completed but before it was opened to all, the king decided to have a contest. He invited as many of his subjects as desired to participate. The challenge was to see who could travel the highway the best. The winner was to receive a box of gold.
On the day of the contest the people came. Some drove fine chariots. Some had fine clothing and fancy food to make the trip a luxurious journey. Some ran the length of the highway to show their skill. All day they traveled the highway; and on arriving at the end, many complained to the king about a large pile of rocks and debris that had been left almost blocking the road at one point, hindering their travel.
At the end of the day, a lone traveler crossed the finish line and walked over to the king. He was tired and dirty but he addressed the king with respect and handed him a small chest of gold. He said, “I stopped along the way to clear a pile of rocks and debris that was blocking the road. This chest of gold was under it all. Please have it returned to its rightful owner.”
The king replied, “You are the rightful owner.”
“Oh no,” said the traveler. “This is not mine. I’ve never known such money.”
“Oh yes,” said the king, “you’ve earned this gold, for you won my contest. The one who travels the road best is the one who makes the road better for those who will follow.”