Archie and Rose McLaverty staked out a homestead where the Little Weed comes rattling down from the Sierra Madre, water named not for miniature and obnoxious flora but for P.H. Weed, a gold seeker who had starved near its source.
Not counting a short epigraph about how many pioneers simply failed and were forgotten, and the subheading 'Archie and Rose. 1885', this is the first sentence of 'Them Old Cowboy Songs' from Annie Proulx's new book of short stories, Fine Just the Way It Is.
An alert reader -- and this is the kind of exercise we used to do in university English Departments while they were still called English Departments and before capital-T Theory took hold -- would be able to have a bash at identifying the date of composition and possibly even the writer.
For example, if you were to set this sentence as such an exercise today, any student lucky enough to have read a bit of Proulx already -- especially if she or he knew there were two different mountain ranges in North America called the Sierra Madre (I've just had to Google this, myself) and one of them is in Wyoming, a state closely identified with Proulx and her work, especially after Brokeback Mountain -- might be able to identify the writer from the setting, from the style, or from the detailed, focused attention to landscape and the inextricable relationship of landscape to character.
(In fact, this is precisely the sort of passage that used to be set in exams as a trap for young players who might confidently mis-identify it as having been written in the 19th century. In the Adelaide U Eng Dept in the mid-1970s they used to do this tricksy business a lot, setting us things like a chunk of very early D. H. Lawrence that nobody had ever actually read, from a time when his style was not yet fully formed, or a poem containing the classical name of a major character in one of the four plays in our Shakespeare course but actually written in 1840, which almost everybody fell for and identified as Elizabethan, a mere two and a half centuries out. In Adelaide we called this kind of exercise Practical Criticism; in Melbourne they called it Dating, which South Australians and Americans thought was hilarious.)
Anyway, the one-word answer to 'What makes this a great opening sentence?' is 'Grammar', but talking about grammar always gets me into trouble so let's look at some other things.
It sets the scene by answering the questions Who, When ('staked out a homestead' points to the time frame) and Where. It comes up with names that manage to sound natural and convincing, a problem all writers wrestle with (though this is easier if you're writing about the 19th century and names like Alice, William, Jeremiah and Mary Ann are there for the taking). It subtly predicts the likely fate of Archie and Rose (look what happened to the last guy), and it suggests the sinister but all too likely possibility that P.H. Weed decomposed into the river: a river poisoned at its source, a powerful metaphor for all things that are doomed from the beginning.