I read an article (maybe on this forum)where they are breeding the hotness out of peppers for Americans because they can't stand the heat. Maybe you ought to try some different seeds. I have found that jalapenos and serranos have gotten milder, I thought I had developed a tolerance to them but am now convinced otherwise. I don't know where you would get "original seeds"

First i'd question my seed sources like river said. Second, if you have really clay soil try liming it. I dunno if that will help the heat or not but it will help fertility. I've also always heard the more you ignore your hot peppers the hotter they get. Could you be over watering?

The only other guess i would have is humidity? Its really humid here in the summer and my peppers are always way way way too hot. All of them. I grow poblanos that are hotter than store bought jalapenos. I'm convinced its just KY's growing conditions because I've grown in rich and poor soil in different locations and years with the same results.

The only reason for adding lime is to raise the pH of acid soils. I'm not sure exactly where in Nebraska you are, but I know where I lived the soil was alkaline and adding lime would only make a more alkaline soil and make many nutrients unavailable.
Also depending on where in NE you live, especially in the Sand Hill area, humidity can be almost 100% all summer and has nothing to do with the heat of a pepper.
Of course species determines how hot any one pepper will be or possibly be, but from my understanding the amount of capsicum created is dependent on air and soil temperatures. The warmer both are the more capsicum is produced. A sandy soil vs. a clay soil will warm much quicker and stay warmer throughout the summer. For example, if the soil has more clay than sand, you might want to not mulch at all or at least not very thickly because while it helps slow moisture evaporation it also prevents the soil from getting too hot at the root level. As an experiment why not try growing a few plants in aluminum or black containers and a few of the same in the clay garden soil? That ought to at least tell you something :)

Good luck

River, thank you for your thoughts. I sincerely don't believe that anyone would go through the expense and trouble to breed the hotness out of peppers or chilies. It's an entertaining thought though.
Pepete, it does get very warm here during the later part of the summer. There seems to be a distinct lack of humidity. And, while our soil has a lot of clay, I don't believe using lime will prove to be advantageous.
Vera, I'm located in the northwestern section of the Nebraska panhandle. You raise an interesting option. I will plant a number of jalapeños in more shallow soil and cover some in plastic. While I don't really expect to realize too much of an increase in the heat/taste, it will be an interesting experiment.
All, if anyone is aware of the best soil ph for growing super hot peppers or knows of anything that can be done to achieve this, please let me know.

Chiles raised for the gringo market are bred to be less picante as we don't really like picante that much.

Redcloud, im from scottsbluff and i do most of my planting in pots now days, my garden space is reserved for the stuff im not to worried about, like corn and onions and such. My babies (peppers and tomatoes)are in pots and my yields are way better than in soil, both in quality and volume.

But when i plant in the ground i prep it with peat moss, and manure. Till it in and spend all summer weeding. Just make sure to keep it well watered, cuz we dont get much rain out here.

And as far as breeding the heat out of peppers, i know a couple people here in the valley that do just that. An older guy i know at the sugar factory likes to pickle jalapenos, but he hates the heat. Hes gotten his peppers down to virtually no heat, really interesting pickle when its all said and done

Why don't they just grow the following variety?

"Fooled You" Jalapeno
(cut & paste into google)

BTW,

We have similar glacial drift silt up here in ol' Dakotey... If anything, the soil here is possibly worse. Yet, my peppers are just as hot as they were when I grew 'em in Texas.

It is hard to say what is goin' wrong with your peppers. I'm sure if you find a way to grow a habanero or two, you'll have plenty of hotness, no?

Whatever you do, don't buy anything that says Jalapeno TAM on it.
http://en.wikipedia.org/wiki/TAM_Mild_Jalapeño

I save seeds from only the hottest and strongest plants each year and it's worked well so far.