+1 for pointing out that the post-War economy was a one-time boom created by the unique situation in 1945.
For the white middle class, life in 1950 was pretty good (unless you were sent to Korea). Life in 1960 was fabulous. At that time, a man could work as a clerk in a hardware store or an assistant in a butcher shop and support a stay-at-home wife and four children in his own middle class home with one car, one television, one phone, etc.
It was the American dream, based partially on generous union contracts for some, and general prosperity for others. Writers were in great demand; musicians could play 365 nights a year. Housing was cheap, jobs were plentiful, and salaries and wages rose every year.
Life in 1970 was different; the Japanese had beaten the Americans at steel, the Vietnam wartime economy was winding down even as Americans perceived we had lost the war, 50,000+ young Americans killed and hundreds of thousands of others traumatized and damaged. The Sixties had taken a massive toll on church, marriage, and society's general cohesiveness and morale, and suddenly things seemed awfully uncertain.
Around that time, Europe and Japan had rebuilt and were starting to compete vigorously, taking away the easy monopoly that American companies enjoyed for the previous 30 years.
It's no surprise that this same socioeconomic group is going through tough times today. The technology economy has no room for people with a high school diploma and good manual labor skills. Some car mechanics in the old days were barely literate, but fixing cars today requires knowledge of digital circuitry and software.
There are some silver linings, though. Shale energy has created a boom for drivers, roughnecks, welders, waitresses, etc. in places like North Dakota. Now that oil is legal to export, and assuming oil goes north of $40/BBL again, the U.S. will probably emerge in another decade or two as the world's largest energy exporter. Cheap domestic natural gas from shale formations has been a boon to the chemical and plastics industries. New technologies such as 3-D printing, as well as rising wages in the 3rd world, notably in China, are bringing manufacturing back to the U.S.
We probably won't see a golden age such as we experienced from 1945-1970, and unions have lost much of their clout since that time, but perhaps there will be more opportunities in coming years for blue collar and middle class workers than since the 1980s. Someone in this thread points out that technology workers may some day find themselves on the other side of the prosperity wall, as well. Nothing lasts forever.