Question
What's the best way to split or cut retaining wall block in half?  I'm using 12" wide x 4" high Windsor cement or concrete block from Home Depot, the kind with a lip on the back that anchors it to the block beneath it.  I'd like to get a nice even, smooth surface on the two halves.  I tried using a masonry chisel on one block
and the result was a very jagged uneven split.

Hopefully, the method will be one that doesn't cost much to implement because I only have about 4 or 5 blocks to split and don't have a lot of power equipment to use for this purpose.

Answer
You need a masonry saw. Rent it from tool rental. They are gas powered.
You can cut one inch and then use a chisel but that will still result in a jagged edge. If you want smooth all the way the only answer is a masonry saw.
Good Luck

www.seanjmurphy.com