Ask Mr. Smarty Plants

Coreopsis lanceolata (Lanceleaf coreopsis) grow in small clumps and are perennials.  The flowers themselves are on single stalks.  They will grow from seed.  Here is more information from Illinois Wildflowers and from Floridata.  You will see from the Floridata page that deadheading encourages more blooms on these plants.  They are often planted for roadside beautification projects.

There are other species of Coreopsis that grow in or near Dane County, Wisconsin:

Coreopsis grandiflora (Largeflower tickseed) is a perennial that self-sows and can become weedy.  The blossom look a lot like C. lanceolata, but is usually taller with different shaped leaves.  Here is more information from Illinois Wildflowers that gives you the differences between this plant and Coreopsis lanceolata.

Coreopsis palmata (Stiff tickseed) has ray flower petals that are more rounded on the end.   Here is more information from Illinois Wildflowers and from Michigan Natural Features Inventory.  It is considered a threatened species in Michigan.

Coreopsis tinctoria (Plains coreopsis) has maroon or red coloring around the central disk.

Coreopsis tripteris (Tall coreopsis) has round petal tips and brownish disk flowers.

Here is a list of invasive species from the Invasive Plants Association of Wisconsin (IPAW).  The IPAW defines an invasive plant as one that:  "both invades native plant communities and impacts those native communitities by displacing or replacing native vegetation."  None of the plants I could see on the lists look like a Coreopsis species.  The IPAW also has a Weedy and aggressive plant species native to Wisconsin list.  Their definition of a weedy plant is:  "A plant that establishes and invades only in seriously disturbed areas (especially in disturbed ground)."  From that list there is one native plant, Helenium autumnale (Common sneezeweed), that somewhat resembles C. lanceolata.  You might also like to check with the Wisconsin Botanical Club (dedicated to the native flora of Wisconsin) to see if they have any information about invasive plants of the Family Asteraceae (Aster Family) similar to Coreopsis lanceolata that have been found in your area.

Probably what you are seeing is either C. lanceolata or C. grandiflora, either of which are plants native to your area.  Even though they are native, they may be weedy or invasive according to your thinking.  If that is so, since neither of these is an endangered or threatened species, you could remove them if you wish.