Soil texture is an important factor in determining the success of your gardening venture.  Texture is determined  by the proportions of sand, silt, and clay minerals of your soil.  Clay, predominate in this geographic area, is very fine-textured, and referred to as a 'heavy soil'.  Clay has one thousand times more surface area per gram than silt, and almost a million times more surface than course sand. 

Sandy or silt loam is said to be the best soil for home gardening, as this provides a mixture  that retains water and is able to percolate and infiltrate.  Clay can become hard as rock and does not drain well. 

Several things can be done to deal with our clay.  One is to add raised beds to your garden, bringing in good loamy soil from a reputable source, and placing it on top of existing soil, where you want to plant. 

Secondly, you can amend your existing clay soil with organic materials.  Two common methods for doing this are: one, to add compost to soil and work it in.  This is best done with hoes and or shovels, as tilling can destroy living organisms, such as worms, which are most beneficial to the garden.  Severely compacted soil may require tilling.  Of so, till down 10-12" deep.   Allow soil to dry out--two to three days prior to adding amendments.  Remove rocks, roots and debris.  Break up any large clods with a hoe.  Place two to three inches of compost on the area and work in.  Do not do this when the soil is too wet or to dry.  Peat moss would work as an amendment, but is expensive.  Compost and well rotted manure both are organic and ideal for garden plots.   A second method  is to cover the area with 4-6" of rotten hay or straw and let it sit for up to a year, as this will slowly break down the soil.  Easier on the back but takes much more time.

A third approach is to accept the clay and plant items that do well in that texture of soil.  Here is a partial list of some flowers that actually will do fine:  Black-eyed Susan, bluestar, aster, baptisia, coreopsis, purple cone flower, sea holly, perennial geranium, false sunflower, daylily, coral bells, blazing star (great for a butterfly garden), bee balm, Russian sage, yarrow, and switch grass, said to actually thrive in moist or dry clay.

So clay does not have to be a gardener's four letter word like mole, weed, or mold.  Work with it, amend it, accept it.