A mature height of about 4 feet is a challenging requirement, at least if you prefer the plants be evergreen to block a view or maintain aesthetic interest in winter. While some species tolerate trimming well, it's always best to select plants that mature close to the desired size rather than rely on pruning, which in addition to chronic plant stress might result in poorer flowering and fruiting in some cases. Dwarf cultivars help greatly with this restriction, but comparatively few of the options suited to this use will have compact selections available or easy to find. We don't have many native evergreen shrubs to begin with, so any other candidate restrictions (such as if they need to be unpalatable to deer) will narrow-down the list even further.

You mentioned they'll receive decent sunlight levels (in summer, we presume?), but does the soil drain well, skew dry, or skew wet (such as from a nearby roof drainage outlet or swale)? We'll list some ideas below to get you started, assuming a full-sun or mostly-sunny exposure, no deer issues, and soil of good drainage. We'll focus on evergreens but will include some deciduous species as well. A laboratory soil test that measures (among other things) soil acidity (pH) may also help narrow-down which species to select in case a particularly notable acidity level or alkalinity (perhaps from leaching concrete or lawn liming runoff) exists in the planting sites; it's always easier to work with existing conditions than trying to alter them to suit certain species.

Whichever species you choose to try, we recommend using a mix and not only one species. Not only will this boost its potential wildlife value and add aesthetic multi-season interest, but it will support the resiliency of the planting as a whole. (Different species won't share all of the same vulnerabilities to various pests, diseases, or extremes of weather, so some can thrive while others may temporarily struggle.)

Evergreens (or nearly so):

• Bayberry/Waxmyrtle (Myrica, now renamed Morella; species M. pensylvanica or M. cerifera...both grow in MD)
  Although the species will probably get too tall, there are several dwarf cultivars, though they might be harder to find. If they are sexed at all, many of these dwarf forms happen to be female, so can produce berries, but at least one male selection will need to be included in the yard for pollination in order for those female shrubs to fruit. Otherwise, if plants are not sexed, it will be pot-luck as to the sex ratio you get when planting several shrubs. Only female plants fruit. These are considered semi-evergreen plants, meaning that they straddle the line between completely deciduous and completely evergreen; it's not uncommon for a few leaves near the branch tips to be retained during winter but older, inner leaves are shed, though this can depend on the weather combined with individual plant genetics.
• Inkberry Holly (Ilex glabra)
  Here too, look for a dwarf variety ('Gem Box' and 'Strongbox' being the two primary options) as the non-dwarf forms tend to mature around 6+ feet high, even if the tags say otherwise. It is normal for Inkberry to lose its lower and inner foliage as it matures because they are naturally not as dense as Japanese and other holly types, though this is supposedly less pronounced on the dwarf varieties. As with the above, plants are either male or female and only female shrubs fruit, though very few male cultivars of Inkberry seem to be on the market so far. Since we are not aware of any males that are also dwarf, and trimming might interfere with flowering, you may want to include one male elsewhere in the yard (or anywhere it could reach 6 feet or so and be fine as-is) for pollination. All are evergreen, but as with many evergreens, a small amount of yellowing and shedding of older leaves is normal for hollies in autumn.
• Eastern Redcedar (Juniperus virginiana)
  The wild type is a tree and thus too big, but dwarf (and as it happens, usually blue-toned) varieties like 'Grey Owl' and "Grey Guardian' are not too hard to find. The former (and probably the latter) produces berries, but not heavily. The value here is probably more from shelter than a direct source of food. Growth will be wider than tall, and while trimmable, junipers do not replace foliage removed from older wood, so this limits pruning to only branch tips and not major branch removal to drastically reduce size.
• Mountain-laurel (Kalmia latifolia)
  A few dwarf cultivars exist that should mature around your desired height, though they are fairly slow-growing. All are best grown with little to no pruning. A "leggy" bare bottom to the branches is natural with age, but more of a factor in non-dwarf selections than dwarf ones. Leggy bases can be hidden with low-growing perennial plantings around their base, if considered an eyesore. They must have acidic soil with excellent drainage to thrive.

• New Jersey Tea (Ceanothus americanus)
• Summersweet (Clethra alnifolia)
  May sucker (spread via stems from root system) if happy, but easy to contain. Thrives in evenly-moist soil and can handle wet conditions well.
• Virginia Sweetspire (Itea virginica)
  The same notes as the above.
• Eastern Ninebark (Physocarpus opulifolius)
  Dwarf cultivars (of which there are several) would fit your height requirements, though those with darker purplish foliage, while showy, might not be suitable host plants for any insects using the leaves as food. Even so, pollinators should still visit the blooms and seeds are also likely of equal value to birds or other animals regardless of summer leaf color.
• Bushy St. Johnswort (Hypericum densiflorum) and Shrubby St. Johnswort (Hypericum prolificum)
  The latter is more tolerant of damp soil; overall, St. Johnsworts are good for drought tolerance.
• Arrowwood Viburnum (Viburnum dentatum) and Witherod Viburnum (Viburnum nudum)
  Dwarf selections of either would provide good berry crops for decoration and for birds provided they are pollinated by another individual of the same species. (Note that two plants of the same cultivar will not be pollen compatible since they are clones of each other. Two different cultivars would be fine.) Here too, if two dwarf types can't be selected, then a taller-grown pollinator partner can be grown anywhere else in the yard that its greater height can be accommodated.
• Blueberry (Vaccinium, several species/hybrids)
  Dozens of cultivars exist, which allows for some customization of choice in mature height; several will be hybrids of more than one species, but whose parents are still either locally or regionally native. For best berry production, include at least two different cultivars in the planting so they will be able to pollinate each other, though they do not need to be direct adjacent to each other. Some have now been bred to not only stay compact but to also produce more than one berry crop or to produce foliage with colorful blushes of pink tones while the leaves are young.
• Black Huckleberry (Gaylussacia baccata)
  May be a little harder to find than its blueberry cousin, but also produces edible berries and using more than one plant should help guarantee decent pollination. The shrubs look fairly close in appearance to blueberry.

Miri