Before you can find morels, you have to know what to look for. By that, I do not mean the signs that the season is here in terms of warmth, moisture, etc (which you can read about in here). I also do not mean the shape or appearance of the mushroom or anything of that sort (don't worry, you can read about morel identification here), but rather the places where they might grow. First, I should note this: there are many species of morels in the midwest. There is the black morel (morchella elata), there's the half-free morel (morchella semilibra or verpa conica), there's the false morel (gyromitra esculenta) and there's the yellow morel (morchella esculenta or morchella esculentoides), and a whole host of other species and subspecies. My predominant focus (and the focus of this article) is on the yellow morel.
Morchella esculenta is a species of fungi which grows in symbiosis with (typically) deciduous trees, particularly the American Elm (ulmus americana), but also including other types of elm, ash trees, sycamores, and poplars, such as cottonwood and aspen (though aspen specifically is more closely associated with black morels). It's not like other fungi which grow on dead wood, like the oyster mushroom (pleurotus ostreatus) or chicken of the woods (laetiporus sulphureous or laetiporus cincinnatus), which consume decaying tree matter. Instead, morel mushrooms (and all mushrooms, in fact) grow from a root structure called mycelium, which is a dense network of threadlike tendrils running throughout the soil called hyphae.
This mycelium grows intertwined with the roots of trees and actually invades the cell wall of the roots of those trees. On a micro-scale, mycelium is offering resources to trees, such as phosphorous and nitrogen and other nutrients the tree is less able to absorb readily from the soil. Meanwhile, the tree shares its resources with the fungal mycelial network as well, such as glucose it absorbs from the sunlight, which fungi cannot do (fungi, generally, are not photosynthetic). In this way the fungal mycelium network grows symbiotically in conjunction with the tree. Fungi whose mycelium grows in symbiosis with trees are called mycorrhizal fungi. Alternately, oysters and chicken of the woods have mycelium growing within the tree itself which eats either the dead matter of the tree or can even cause the tree to die slowly. Mycelium which grows on the dead or decaying matter of plants are called saprophytic fungi. So the two main types of mushrooms which you would be interested in eating are typically either mycorrhizal or saprophytic.
Morels, as noted before, are mycorrhizal. Also, unlike some of the other mycorrhizal fungi, they do not fruit quite so readily. Healthy morel mycelium living symbiotically with a healthy host tree often have no need to fruit mushrooms. To fruit mushrooms is that organism expressing its desire to spread its seed to find a new place to live. When its "host" tree (even though this relationship is not parasitic, I'll use that word for convenience sake) is healthy, the mycelium is healthy. When its habitat is healthy, the mycelium is healthy. Morels do not typically fruit when this is the case. However, when its host tree appears to be dying, the morels will say: "uh, guys, we gotta get a new spot, this tree ain't gonna make it!" And out will pop a bunch of mushrooms to spread their spores.
The most famous example of this is when old-timers tell you that to find morels you gotta check under dead elm trees. This is true! Back in the day, when elms first started dying off all across the midwest because of Dutch Elm's Disease (ophiostoma ulmi), which perhaps ironically is a parasitic and saprophytic fungi, morels fruited prolifically. Those same old timers will tell you stories of filling trash barrels full of morels in 30 square feet! Now that there are less elms throughout the countryside and the woods, morels are much more rare. But there are still new, young elms growing all the time and old elms dying off, too. So to find morels, it is monumentally important to be able to quickly and accurately identify dead elm trees. Suddenly, instead of wandering through the forest and looking under every tree, you'll be wandering through the forest and looking, intently, only under the trees that are likely to fruit morels.
So, after that longwinded diatribe on mycelium and symbiosis, let's get down to the nitty gritty: how to find some good spots for morels. First, look at the forest around you. If you are surrounded by an even stand of oak savanna, there's not likely to be a bunch of elms around (although on the edges of these forests you can find lots of elms). When I am finding a lot of elms, they're usually located around a lot of maples, basswood, and oaks, too. There should be a diversity of trees. Consistently, elms are located on the edges of forests, prairies, farmland, and sometimes along the edges of rivers or bogs. These are also often the easiest to spot due to an open unobstructed view.
Elms have the shape of an upside down witches broom. That's the classic dead elm shape. Sometimes they are not in that shape and also sometimes a tree is that shape and not an elm, but that's a really good, helpful starting point. Next, if you want an elm that will fruit, find ones that still have some of the small branches. If they're so dead that they've lost all but their largest branches, it's probably too far gone to fruit any mushrooms (except it may fruit saprophytic fungi like oyster mushrooms). Same goes for bark, as in, there should still be some.
If big chunks of bark have come off, you still might be okay, but if the tree is bare of bark completely, don't spend too much time hunting around that tree. You might still give it a once over, just in case. A couple other helpful tips, if you're standing there and staring at what you think might be a perfect dead elm but aren't sure, look at the branches. If the twigs grow in an alternating pattern, you're on the right track, unlike maples which grow opposite, as in two stems will come off of a branch at exactly the same point, just opposite one another. For alternate, a stem will grow on one side, then go up an inch or two or four and there will be a stem on the other side. Almost like zig-zagging. A last note on elm ID is its bark. It does not have deep furrows like cottonwoods or oak trees. It doesn't have smooth bark like beech trees or some maples, either. It has lightly furrowed, scaly bark. If the elm is really big, like too big around to wrap your arms, it might have deep furrows, but this is not a common tree to find other than on a street boulevard! I highly recommend picking up a tree guide (I use Audobon Society and it's great). Knowing your trees is crucial to becoming an expert mushroom hunter.
A couple of other notes: folks tell me they find morels around live ash trees or cedars or river birches, etc. I have found them near ash, but usually it's because there's a dead elm nearby. I do not doubt that they grow symbiotically with ash trees but it's unusual (in my experience) to find a lot of morels near ash trees. Also, down south, there's morels that grow under live sycamore trees. I've found them in those habitats and it's a lot of fun! With that said, it can be really hard and I almost wonder if I didn't just get lucky one time. Generally, finding morels under dead elms has, in my experience, led me to find pounds upon pounds every season for the last five years here in Minnesota, so give it a shot if you're struggling. If you find morels by ash, and that works for you, by all means keep doing it!