How old was Robert Frost when he wrote the road not taken?

Robert Frost was 49 years old when he wrote "The Road Not Taken".

He published the poem in 1916, and it was first included in his collection *Mountain Interval*. Frost was born in 1874, so he would have been 42 when he wrote it. However, he revised the poem many times before its publication, making it difficult to pinpoint exactly when he finished the version we know today.