The Jacob's Ladder Quilt Block is a classic, and there are many variations of it.  It also has other names, such as the Underground Railroad.

As you can see from the picture at the left, this is a 9-patch quilt block.  Some of the patches have been further subdivided into 4-patches.

What distinguishes a Jacob's Ladder Quilt block is the four large half square triangle quilt blocks that are placed so as to give strong diagonal movement in the block.  Most of the variations of this block are in the smaller squares and have to do with whether or not they are subdivided and where the dark squares in the smaller 4-patches are placed.  You can continue the movement in the same direction, or you can turn them so the movement is in the opposite direction.

This version of the Jacob's Ladder is easy block to construct, as it is made from all half square triangles, or 4-patches.  When you place the squares, be sure the middle block is placed as shown, so that the 4-patch continues the strong diagonal movement established by the large half square triangles. 

Notice how the diagonal movement of this block is accentuated by using a sharper contrast in value in the block on the left compared to the other blocks on this page. 

This block is often placed in sampler quilts.  Here is a visual of this block with a few other 9-patch blocks.