I can answer this from a European perspective at least:

The concept of Liberal and Conservative developed during the Enlightenment, so I'm going to reframe the terms. We'll say Progressive (that is, desiring change) and Conservative (that is, desiring that things not change).

Agrarian societies tend to dislike change. They rely on a long term investment of resources and energy to produce crops on which they have to rely for the whole year. A change that is not beneficial can mean death. This does not mean that farmers do not innovate, they do, but they do so slowly. This means that rural areas, which historically have been dominated by farming and still are on a global scale, tend to be very Conservative. They only change when something no longer works. The exception to this is when people are expanding and settling in to new, previously uncultivated areas such as during the High Middle Ages when forests were cleared or during the American Colonial and Westward Expansion movements.

The Urban centers that emerge during the High Middle Ages tend to be centered around trade. In a market, innovation tends to pay off and investments can be mitigated or recouped at a greater rate than can be done with an agricultural growing season. This doesn't mean that people who took risks didn't fail, but instead that those who succeeded did so at a rate which would have been largely impossible for their agrarian counterparts.

Because of this, change happens more frequently in cities. Cities also tend to be exposed to a greater variety of cultures because people move to them for trade (rather than away from rural areas to trade in towns and cities before, hopefully, returning home). This exposes a greater number of issues which need to be resolved (from traffic to how to deal with this new "merchant nobility") and thus means that cities tend to favor a Progressive approach, at least relative to their hinterlands.

Further reading: For agricultural innovation, I would take a look at Balestracci's The Renaissance in the Fields.

There are a variety of works on medieval and Renaissance urbanization, but I'm particularly fond of "Medieval Towns: A Reader" as the primary documents are both comprehensive and topically relevant.

In order to answer this you would need a sufficient transhistorical definition of "liberal" and "conservative", which I suspect is rather difficult to get. But I suppose to answer the intent behind your question, there have been numerous examples of radical political movements that originated or found their greatest roots in the countryside. The various peasant revolts of the Middle Ages would be one example, or in more recent times, the way that agricultural workers were a lynchpin of the American communist movement. And sometimes there is a complex interplay between town and country: for example, the argument could be made that the French Revolution only became radicalized with the Great Fear peasant uprisings.

And if you are thinking in terms of cultural conservatism, there are numerous examples of well educated urbanites going to the countryside and being shocked at the barbarous and heretical customs (and this still happens today--think of the VICE style documentaries where some "journalist" goes to the Appalachians to gawk at the craAaAaAazy religious rites).

But I think a broader answer to your question might relate to the historical examination of rural political activity. And in this I follow the anthropologist James Scott: the nature of rural society, such as its demographic dispersal, means that the political options facing it are rather limited. Peasant uprisings exist, but they tend to be a very last resort because the common result is the slaughter of the peasants. Instead rural political activity is largely confined to smaller scale activity, such as non-compliance, petty sabotage and foot dragging. These can add up to major effect, one might think of how Charles I's campaign in Scotland was hamstrung by wide scale noncompliance, but it very rarely can make its way into the sort of archival documents visible to historians. Ultimately it makes it very difficult to understand the political orientation of people in the past.

This is likely impossible to answer in the terms that you're currently asking for, because areas developed differently at various times. Might I suggest you amend the scope of your question?

A couple followup questions:

Are there different reasons behind these distinctions for political conservativism (or progressivism) compared to for religious conservativism, or does political and religious conservatism correlate strongly enough to not distinguish the reasons behind how progressive a region is?

I've heard hypotheses that compare the nature of religious sects to the environment in which they develop. E.g. gentler, more grace-oriented versions of Christianity coming out of more fertile, easier to farm lands and harsher, more judgment-oriented versions coming from less forgiving geographies and climates. Does that line of thinking have any traction within the broader academic community?