Split a Variable Sequence at a Specific Value

This is a very basic question:

I have a variable sequence as a domain, generally including both positive and negative real numbers. I want to split the sequence at 1.0, and the index of this value is uncertain. How do I retrieve 1.0 and use it to split the sequence into two domains, one being all x < 1.0, the other being all x >= 1.0?

It's seems fairly straight forward but it's taking me some time to find the right method. If anyone can share some insight, I would appreciate it very much.

-Seth