Plant taxonomy classifies American sweetgum trees (also spelled "sweet gum") as Liquidambar styraciflua. The sweetgum tree I recommend is Liquidambar styraciflua 'Rotundiloba,' a sterile, non-fruiting culitivar.
American sweetgum trees bear leaves shaped like stars. The leaves provide excellent fall foliage color: in some cases, at the peak of the fall foliage season, some leaves may be red, others purple, others yellow, others orange -- all on the same sweetgum tree! On some trees, the branches are "winged," as on winged euonymus (burning bush), displaying corky flanges. Most people consider their seed pods (or "fruits," "balls," "gumballs," "capsules") to be messy, so I recommend the fruitless 'Rotundiloba.' Rotundiloba grows 60'-70' tall with a spread not even half that, which helps give it a narrowly pyramidal form.