I'd say one of the biggest reasons for the disappearance of hardtops was the widespread application of automotive Air Conditioning.

On of the main reasons for pillarless bodies was the fact that they opened up the whole car interior and improved ventilation, especially in the hot summers in most of the US.

By the 70's A/C was becoming commonplace, and the need for 2 or 4 open windows was going away as we all became comfy in our air-conditioned cocoons. Remember the Mercury Breezeway?

today, almost every car is equipped with factory air, and there's little need to open a window for fresh air; and the cabin air filter keeps the interior air fresh, and keeps dust and bugs out.

While changing tastes are certainly a part of the demise of the hardtop, I propose it was the humble air conditioning compressor that killed them off.

I think that was a factor, but I don't think it was the primary reason, particularly for high-end cars like the Eldorado and Continental Marks, where the take-up rate for air was already quite high by the late sixties.

Also, I don't think the ability to roll down all the windows was nearly as important to the popularity of hardtops as style. Particularly on a lot of early-seventies hardtops, with their extreme tumblehome, opening the side windows even partly tended to create massive buffeting; it wasn't that practical for ventilation unless you spent a lot of time under 35 mph.

The biggest contributor to the demise of the hardtop was the strengthening of federal rollover crash standards for the 1974 model year. 1973 was the last year for hardtop coupes in the General Motors full size lines. Hardtop four-door sedans were gone by 1977. Air conditioning really didn't have much to do with it.

That is a popular explanation, although my research suggests that it's only partly true.

After originally posting this article, I looked up what the federal standards actually are. The standards to which people are generally referring when they talk about this are 49 CFR 571.216: Federal Motor Vehicle Safety Standard No. 216, Roof Crush Resistance. As actually enacted (an important point that I'll get into in a moment), FMVSS 216 went into effect for passenger cars (i.e., vehicles with a GVWR of less than 6,000 lb/2,722 kg) on September 1, 1973, the beginning of the 1974 model year. Under the standard, the vehicle's roof must not deform more than five inches (127 mm) when subjected to a vertical force equal to the lesser of 1.5 times its empty weight or 5,000 lb (22,240 N). Convertibles are exempt.

The effective date of that standard means that a fair number of hardtop coupes did indeed meet that requirement. (There were no phase-in provisions, and no exemptions other than convertibles and vehicles over the GVWR limit.) Until very recently, that was also as stringent as it actually got; new rules have been enacted, but the phase-in process doesn't begin until MY2013.

However, from what I've been able to gather, the version of this standard that was originally mooted was a good deal more stringent than what was actually enacted. (The AMC Pacer, for instance, was designed with provisions for an integral roll bar through its B-pillars, in anticipation of those rules.) All of the FMVSS were the focus of intensive lobbying and occasional threatened or actual legal action by automakers, and there was considerable political pressure on both sides. Sorting out the details of what was originally proposed and how it evolved is complicated at this remove, and would probably involved some hard time in front of a microfilm reader, but it's likely that the existing regulation was a compromise.

In any case, I think it's probably reasonable to say that the decision to phase out hardtops (and convertibles; I gather that the exemption in that case was a late change) was strongly influenced by the proposed regulations, and by the time the somewhat less stringent actual regulations were decided, styling decisions had been made and tooling had been bought. The Pacer again is probably a revealing example -- the B-pillar design didn't change, even though the production cars didn't actually have the roll bar. And after that, designers and product planners not in the habit of leafing through federal regulations over breakfast may have just assumed that the game had moved on, and pursued other themes.

Amen, Admin on 70's frameless glass and buffeting. GM "Collanade" intermediates being a notable offender. Practically, the mechanisms for holding the glass in place became less robust on most makes, hitting a nadir on GM mid- 80's G bodies and 95 through 99 Neons. Flap city.
Long after they were gone from these shores, the Germans, in the form of the lovely W124 chassis CE coupes, kept the pilarless hardtop alive.

The BMW E31 8-Series was also a pillarless hardtop (as were the earlier E9 coupes), but BMW hasn't been as consistent with pillarless models; the E63 6-Series is not, nor, I believe, is the new F13.

An enjoyable entry as always - but it seems to me that the decline of "the hardtop aesthetic" deserves further analysis. It may be true that "many American preoccupations of the time [the 1970s] demanded a certain privacy" (if people wanted privacy why didn't they go indoors?), or that something about the political nature of the 1970s was involved as you suggest. But there are much earlier instances of more "intimate" greenhouses - for instance, the two- and four-door 1962 GM full-size hardtops and sedans (versus the very similar but larger-windowed 1961s) - as well as much later examples, such as the K-car-derived New Yorker and Imperial sedans of the early 1990s still sporting opera windows (built into the rear doors) and wrap-over rear roof treatments.

Like hardtops, blind quarter panels and formal roofs were not at all new -- they were common on limousines, of course, and were prominently featured on a lot of the Derham customs and semi-customs of the forties and fifties. They popped up here and there on mainstream cars -- the GM cars you mention, the early-sixties Imperial LeBaron, and so on -- but it wasn't until the seventies that they really became ubiquitous. Likewise, the idiom held on into the eighties and early nineties, with a whole range of Chrysler products that all looked vaguely like miniature Mark Vs, but by then, they were really rather anachronistic. You still occasionally see cars with aftermarket coach tops that blank off half the quarterlights and a third of the rear window, but they're the anomaly, rather than the norm.

One could always say that the transition to the seventies pseudo-landau/brougham look was a shift from cars that looked sort of like sporty convertibles to cars that looked sort of like limousines. Certainly, the desire to look affluent is a major driving factor in a lot of automotive trends. On the other hand, the eighties were nothing if not wealth obsessed, but I think most affluent Boomers tended to turn up their nose at seventies-style symbols of luxury, so it wasn't JUST that.

As for your other point about just staying home, well -- in the seventies, people did an awful lot in discos, bathhouses, and custom vans that one might ordinarily expect to fall into the 'privacy of your own home' category...

Hi Aaron,

The hardtop Hillmans were the Californians (and Sunbeam Rapiers), not the 4-door sedan Minxes. The roofs on the Californians at least were effectively welded-on hardtops on a convertible body shell in those years.

Another interesting curiosity was later versions the 1948-54 Sunbeam Talbot 90 sedan (eg Mk3) which had a suicide rear door without a C pillar, just overlapping glass.

Oops! Thanks for the correction.

I live in Brazil, where only two hardtop coupes have been made: the Dodge Dart/Charger (built 1969-81), based on the 1967-69 A-Body Dart, and the Chevrolet Opala (built 1971-89), based on the German 1967-71 Opel Rekord body, but powered by inline 4- or 6-cylinder Chevrolet engines (153/151 CID or 235/250 CID).
From 1980 to 1982, my parents had a 1978 6-cylinder, dark blue Opala hardtop coupe. I absolutely loved it. When they decided to sell it, I made a drawing of it as a souvenir and, unaware of anything (I was 15 at the time), wrote its VIN at the back of the paper sheet. Thanks to this - and Google -, I was able to find the car in March 2009; it had been impounded about two years before, and was going to be auctioned and scrapped. I bought it back and restored it from the ground up. Today, I'm glad and proud to say it's turning heads at the streets again, just as it did 30 years ago!