Spoilers, maybe (?)
This is often cited as the 'beginning' of film noir. I can't say for certain or not if there's another film before it that predates it - and of course there were not one but two adaptations of the Hammett book prior to the 1941 version (I actually didn't know about the 2nd with Bette Davis until tonight) - but I can see why that is, and it's because Mary Astor is such a striking, perfect femme fatale, and Bogart makes the persona we all associate with Bogart.
Who do I mean by that? I feel like it's the guy who's smart, really smart, but not in the way that is bad or cruel, more like intuitive, ahead of the curve, and able to give a good remark when needed. You see that in Casablanca (to a more lost-romance extent), To Have and Have Not (more conventional romance), and even Treasure of the Sierra Madre (where he can still make cutting remarks, but it's more about greed and the dark side as the Force says). This is Bogart in full bad-ass mode, the first part of the double LP that would continue/conclude with The Big Sleep as Marlowe (kind of the same, though more in deep shit). Seeing him in this again after not seeing 'Falcon' for quite some time, I was reminded how totally in command Bogart was here - and it's good he was as broke the mold of being the criminal/gangster from years of being typecast. He got typecast in another way, but really why carp?
I'm not sure if this is a "film" in the sort of speak of movies vs. films - that is, how much do you take something made in Hollywood in the studio system as full on art vs being a product - but it's simply grand entertainment any way you look at it. I'd actually point to this just as much if not MORE (damn I'll say it, come at me film bros) as THE example of how to make a classic Hollywood movie of the period it was made. It has comic lines, it has romance (and innuendo, of course, and it slips by with such amazement as its from 1941), and a little action and suspense (punches are thrown, but it doesn't have to be too violent). And all the while it's actors - character actors, mostly, even Bogart was up to a point, but here it's the mother-lode - eating up the delicious dialog from Huston via Hammett for all its worth, with Greenstreet getting the meatiest of the monologues (though Lorre gets a line delivery at a crucial revelation that practically created the character of Ren on Ren & Stimpy).
It's tough and hard-boiled, but it's not so dark that it's some sort of chore to watch like if it goes around in too many circles. You have to watch it, and pay attention, but it's never so confusing if you know, as the Ebert axiom goes, *how* it's about it. By that I mean, it's a movie about storytelling, the yarns that are pulled around and how characters try to play one over on one or someone else, or maybe everyone. Indeed with the exception of Elisha Cooke Jr's character (and damn is it great to see him here), everyone is playing someone for a fool at one point or another, and it all depends on style. On the one hand you got the "school-girl" schtick of Astor's Brigid, and on the other you got the sort of sophisticated, maybe-British-but-more-Euro-something drawl of Greenstreet.
And in the center of it you got Spade as a guy who has to stay ahead of everyone, and yet seem like he's in with them the whole time. Of course the story takes twists and turns, and it wouldn't be so memorable if not for the reveals. But what struck me seeing it this time was just how outstanding the ending is. I won't spoil it for... oh screw it, you know what I meant by 'femme fatale', right?
Of course it has to work like this, regardless of what the Code would've had to say for the time if, say, Brigid had gotten away with her crime(s). But it makes it kind of tragic in a weird way, or perhaps it's by how Bogart has that sort of mile-long stare that he had perfect here even before his drunken malaise conversation with Ilsa in the bar in the middle of the night a year later. He and Astor as so good it makes me almost mad that actors or endings aren't good like this today, that there isn't this sense that 'yes, it has to be this way... and why?'
In short, the "first" film-noir bad-ass and femme fatale in a pairing that makes for one of the milestones of the medium.
(PS: If I had seen this in 35mm instead of a Turner Classic Movies projected DCP, or blu-ray or whatever it's called, I wonder if a few of the fuckers in the theater with me would've been quiet instead of acting like it was their living room... one can hope, can't we? A quiet theater is what dreams are made of, after all...)