Two things:

1) Industrialized Warfare

2) Social Safety nets (social security, medicare, etc.).

The reason why it takes two to have what is considered a middle-class lifestyle is because we have raised the bar on what constitutes a middle class lifestyle.  If you have 3 families and 2 of them have wives who decide to go into the workplace then those two families will earn more. The median income will thus rise and the third family, who hasn't actually lost anything, will be described as being poorer because they are poorer relatively.

Incidentally, one would have to have a mortage over over $350,000 for the mortgate payment to be over $2,000 per month.  A $350,000 house will get you typically a 3,500 square foot house ($100 per square foot national average).  The cuople in 1941 lived in a house that was less than 1/3rd that size.   The funny thing about statistics is that dumb people are easily confused by them.  Be wary of falling for "median" and "average". 

Quick look on the Internet:

What Things Cost in 1941:
Car: $925
Gasoline: 19 cents/gal
House: $6,900
Bread: 8 cents/loaf
Milk: 34 cents/gal
Postage Stamp: 3 cents
Stock Market: 111
Average Annual Salary: $2,050
Minimum Wage: 30 cents per hour

Go back and find houses from the 1940s and you'll find houses that are around 1,000 square foot as being average. That would be around $100,000 in today's dollars.  If you're going to play with statistics, do apples and apples. A $15 mortage would only be for a $2,000 mortage which is 1/3rd your claim (I mean you can't even keep your numbers straight within a single sentence? How lazy are you?). The average new home in 2001 (when they were over-valued) was about $200,000. That's for a 2,000 or so square foot home -- twice the size. The median single income is around $30,000 today. 

The net of this is that how much an individual can buy today has grown significantly since 1941 and it's of much better quality.  The fact is that it doesn't take 2 to make due. It's just that most Americans are not willing to live like they did in 1941. They want the 2,500 square foot house, the two cars, the annual vacation, the kids going to Soccer and other non-free activities, along with the other modern conveniences that come with disposable income.

Some people (We call them Democrats) worry far too much about how much other people make as if someone else having more hurts them.

At 11 acres you're paying for the house and the land.  Most houses are on a 100 x 100 lot. That's in feet.

Col Gene:

The average house price in the US is not $300,000. That's crazy.  As others have linked to, there are sites that will tell you the average price.

Moreover, even a $260k mortage at 5.9% interest is a $1,500 payment:

http://client.aavirtualoffice.com/calculators/Mortage-Results.asp

Mortgage calculators are easy to find.  You will have a hard time making the case that the average American today isn't far better off than the average American in 1941. 

We don't NEED two peple to work.  We WANT to pepole to work so that we can afford all the goodies out there that weren't available in 1941 (DVD players, computers, fancy laundy machines, dishwashers, much larger houses, 2 cars, televisions, cable, Internet, etc. etc. etc.).   You also ignore the fact that many women simply want to work.  We live in an age where laundry and food preparation don't involve hours of work per day. There's a lot more time available and many women are choosing to go to the work place. I say good for them.