Solitary People
Just about everything Wordsworth ever wrote in his prime has some kind of solitary figure just kind of… wandering around. And by "everything" we mean pretty much everything. We've seen how "The Solitary Reaper" features a—wait for it—solitary reaper, but here's a quick run-down of a few others. In "Resolution and Independence" (published in the same volume as "The Solitary Reaper"), the speaker encounters a solitary leech gatherer (worst job ever). In his epic poem "The Prelude," the speaker meets with a number of different "loners," from a discharged soldier in Book IV to the lonely dead body of a drowned man in Book V.
A lot of times, the solitary figure is the speaker or poet himself. Many of Wordsworth's poems can be described as just a man and his thoughts. This is especially true of some of his most famous poems, such as "Lines Composed a Few Miles Above Tintern Abbey" and "Ode: Intimations of Immortality" (also from the same volume as "The Solitary Reaper").