Ask Mr. Smarty Plants

One of the main reasons you don't find turf grass mixes made entirely of native fescues is that most of the fescues are strictly bunch grasses—without rhizomes (underground horizontal stems) or stolons (above ground horizontal stems) that enable the grass to spread easily to adjacent areas. For bunch grasses to spread to bare spots and adjacents areas they have to be seeded.  There are not enough native Festuca species with rhizomes and/or stolons to create a good mixture for ecograss.

Here is an excellent treatment with a key and descriptions of the Festuca species from Utah State University Intermountain Herbarium.

The fescues (Festuca spp.) occur worldwide.  You can see the species that are native to North America by clicking the Subordinate Taxa tab in the menu of the USDA Plants Database page for Festuca L. (fescue) and looking at the distribution maps for the various species that have been recorded.  Of the North American natives that occur in the lower 48 states, there are only 5 species that have rhizomes.  There are four species with short rhizomes:  F. altaica, F. earlei, F. hallii , and F. ligulata.  F. pseudovivipara (that occurs in Canada in British Columbia) and some subspecies of native Festuca rubra (Red fescue) have true rhizomes. Also, some subspecies of F. rubra have stolons.  The USDA Plants Database distribution map shows that there are both native and introduced subspecies of F. rubra. By clicking on the Subordinate Taxa tab on that page you will see which subspecies are considered native and which are deemed to be introduced.  As you might suspect, there is controversy about some of the designations of nativity, plus there are hybrids that occur between the subspecies.

I've searched for the seed mix used in these eco grasses and have been unsuccessful in learning the botanical names of the grasses in most of the mixes (e.g., Eco-Lawns from Wildflower Farm, Eco-Grass from Prairie Moon Nursery, SeedSuperStore mixes).  Common names are not a reliable way to search for and learn nativity of plants. Many of these mixes list "fine fescues" as a major component. Colorado State University Master Gardener Program has an article, Fine Fescue for Lawns, that lists the advantages and disadvantages of fine fescues for turf grasses.  The grasses listed in their article are:

Festuca brevipilia [synonym = Festuca longifolia](Hard fescue) and Festuca ovina (Sheep fescue)—both introduced species—and three subspecies of Festuca rubra (Red fescue)—Festuca rubra ssp. fallax [synonym = Festuca rubra ssp. commutata] (Chewing's fescue) is introduced; Festuca rubra ssp. litoralis (Slender red creeping fescue) isn't listed on the USDA Plants Database; and only Festuca rubra ssp. rubra (Creeping red fescue) is native.

 For reference to your state, the USDA Plants Database lists four Festuca (fescue) species native to Iowa:

• Festuca rubra (Red fescue) is a variable species with many subspecies that occur worldwide with some subspecies considered native to North America and while others are not.  Some of the subspecies are known to be mostly bunch or tuft grasses while others of them, e.g., F. rubra ssp. rubra, have rhizomes and/or stolons and are considered creeping grasses. 
• Festuca saximontana (Rocky mountain fescue) does not have rhizomes. 
• Festuca subverticillata (Nodding fescue) does not have rhizomes. 
• Festuca paradoxa (Clustered fescue) does not have rhizomes.