William Swan Plumer loved to write theology for the common man. Many of his books were aimed at the church at large, not merely pastors or scholars. Toward the end of his life, Plumer published Truths for the People: Or, Several Points in Theology Plainly Stated, for Beginners (1875). If you or someone you know is looking for a book that hits the highlights of systematic theology, but in an accessible style, in short chunks and even shorter sentences, then this is the book to read.
What would it have been like to sit in Archibald Alexander's class on Systematic Theology in the early days of Princeton Theological Seminary? Fortunately, Princeton has scanned in Charles Hodge's notes from that class - just think, if you had been sitting next to Charles Hodge and snuck a peak at his notes, this is what would you have seen. It's a remarkable thing that we have these, but I'm sure there are many other manuscripts of classroom lecture notes (and professors' lectures!) holed away in archives around the country. If you know of any others that are accessible online, please let us know!
Most pastors and seminary students are aware of Charles Hodge's three volume Systematic Theology. It is one of the most recognized works of the 19th century, and can be purchased here. But this set certainly was not the only systematic theology published by Presbyterians in the 19th century. Sometimes remembered are William Greenough Thayer Shedd's Dogmatic Theology (you can purchase the modern edition of this book here) and Robert Lewis Dabney's Systematic Theology (you can purchase the Banner of Truth reprint of this volume here). Very few people know that Robert Jefferson Breckinridge published a two volume systematic theology, entitled The Knowledge of God Objective Considered and The Knowledge of God Subjectively Considered.
Older systematic theologies weren't asking all the same questions we ask today, of course - but that's a big reason why they are so helpful to use. They ask questions we don't even know we need to be asking. So the next time you're wrestling with a theological question, dip into one of these volumes and see what riches you might find.