Arkansas is a land of mountains and valleys, thick forests and fertile plains. The so-called Lowlands are better known by names of their two regions, the Delta and the Grand Prairie. The Arkansas Delta is a flat landscape of rich alluvial soils formed by repeated flooding of the adjacent Mississippi. Further away from the river, in the southeast portion of the state, the Grand Prairie consists of a more undulating landscape. Both are fertile agricultural areas.

The Delta region is bisected by an unusual geological formation known as Crowley's Ridge. A narrow band of rolling hills, Crowley's Ridge rises from 250 to 500 feet (150 m) above the surrounding alluvial plain and underlies many of the major towns of eastern Arkansas.

Northwest Arkansas is part of the Ozark Plateau including the Boston Mountains, to the south are the Ouachita Mountains and these regions are divided by the Arkansas River; the southern and eastern parts of Arkansas are called the Lowlands. All of these mountains ranges are part of the U.S. Interior Highlands region, the only major mountainous region between the Rocky Mountains and the Appalachian Mountains. The highest point in the state is Mount Magazine in the Ozark Mountains; it rises to 2,753 feet (839 m) above sea level.

Arkansas is home to many caves, such as Blanchard Springs Caverns. It is currently the only U.S. state in which diamonds are mined.

The United States imposes an income tax on individuals, corporations, trusts, and certain estates. This tax is imposed on the income event, such as the receipt of wages. Another example of an income event is the realization of a gain on the disposition of property; that is, the appreciation on the value of property is not taxed until that property is sold (i.e., when the gain is "realized").

The U.S. income tax was first proposed during the War of 1812, but was defeated. In July 1861, the Congress passed a 3% tax on all net income above $600 a year (about USD 10,000 today). Income taxes were enacted at various times until 1894, but were not imposed after 1895 after an 1894 tax act was found to be unconstitutional. In response, the 16th Amendment was ratified in 1913. Ratification has been unsuccessfully disputed by some tax protestors claiming, among other things, that slight errors in punctuation in the various instruments ratified by the several states invalidates the ratification. Tax protestors have also made other arguments about the validity of the U.S. income tax, without success.

The 2007 individual federal income tax rates are between 10% and 35%, depending on income and family status. People with relatively low incomes may pay no income tax, or may receive earned income tax credits (tax benefits); however, this does not include income based payroll taxes that fund Social Security and Medicare. The Center on Budget and Policy Priorities states that three-fourths of taxpayers pay more in payroll taxes than they do in income taxes. IRS data indicate that the wealthiest 5% of taxpayers (ranked by AGI) paid roughly 60% of all income taxes; the bottom 50% of taxpayers account for just 3% of income taxes paid.