I believe Charon has the issue pretty well nailed.
If I'm reading his posts correctly, the voters in Illinois are divided on the gun issue not so much along political lines as they are along urban and rural lines.
Tellingly, this coincides almost perfectly with the urban vs. rural split on conservative vs. liberal politics.
If you think about it, those are not contradictory statements. There are plenty of Democrats who vote conservatively on some issues because of their rural backgrounds. How else can one explain state voters who normally vote Democratic on many domestic policy issues rotating 180 degrees to vote Republican on issues such as abortion and gun control.
Conversely, some urban Republican voters will vote almost in lock-step with their Democratic "opponents" on certain issues while Republicans in rural areas will adopt opposing stances on those same issues.
Thus, gun control is a hot topic in most large cities and urban states. Yet, the same issue can gain almost no traction in those states that have large rural populations.
Why is this? The issue has very little to do with one group being more intelligent or enlightened than the other. Rather, in my opion, the issue is largely cultural. Southern and western cultures have always had firearms available for sporting, recreational, and defense uses. They are seen as an extension of a fiercely independent citizenry that loves and supports their country but doesn't completely trust it's government to respect its constitutional rights.
Many people in the urban population have, on the other hand, little actual connection to, or understanding of, rural culture and its traditional attitudes about gun ownership for recreation and defense. The fierce independence of rural citizens is, in the case of urbanites, often funnelled into other areas and interests. Long separation from farming and other traditional lifestyles has given rise to an urban mindset that can no longer identify with rural culture or its mores.
In return, rural regions find the fast pace and more liberal mores of urban culture to be repugnant.
The sad thing about this urban and rural split is that neither side makes any real attempt to understand the other. Meaningful debate and attempts at reconciliation become, instead, rancorous and bitter arguments that add nothing meaningful to the national dialogue on the issue.
The debate over gun control is just one symptom of a split that threatens to permanently produce two Americas diametrically opposed to each other along political and cultural lines.