Elderberries are delicious and a wonderful way to fight disease, but they are also hard to find if you don't look for them at the right time (or don't realize what you're looking at). It took me years and the help of the Foragers Unite! group on Facebook to finally start seeing them.
The University of Minnesota extension office says:
The common or American elderberry is a shrub growing from 4 to 12 feet tall. It is found in moist soils along roadsides, ditches, streams, and in fields. It has creamy clusters of tiny star-shaped flowers that become round, purplish-black berries in late summer and early fall.
That sums it up nicely. Take care when harvesting elderberries, as some parts of the plant are poisonous and they frequently grow around plants like nettle (one of my favorite patches is intermingled). And be sure to visit the elderberry.com Facebook page.
When you DO find your elderberry plants, mark them down so you can find them when they're ripe. One good option is to take a picture of the area with your digital camera and log it (being sure to include any landmarks), use a foraging app, or use Google maps.