The film's title comes from the poem "Stopping by Woods on a Snowy Evening" by Robert Frost, first published in 1923: The woods are lovely, dark and deep, But I have promises to keep, And miles to go before I sleep, And miles to go before I sleep.
The word Coimbra is carved into the wood in the ranger's cabin, among many other names. And the name of one of the executive producers is Stefanie Coimbra.
The book Lennon is keeping her sister's picture in is a volume of Missing 411, which chronicles mysterious missing persons cases in national parks. Lennon's call number is 114.