I was looking more at Liouville numbers. This Wikipedia link seems to contain the basic information along with a proof that these numbers are transcendental:
https://en.wikipedia.org/wiki/Liouville_number
The proof depends on the concept of the "irrationality measure" of a number which is a measure of how close the number can be approximated by rational numbers. Rational numbers have an irrationality measure of 1. Basically, they are not irrational. Algebraic numbers that are not rational have irrationality measure of 2. Transcendental numbers have an irrationality measure of 2 or greater. Liouville transcendental numbers have infinite irrationality measure. They are kind of extreme as far as this measure goes. It looks like they were constructed to make sure they were as far away from being algebraic as possible which allowed them to be more easily proven to be transcendental.
The algebraic numbers are roots of polynomials with integer coefficients. They include the rationals which are roots of linear polynomials f(x) = rx + s where r and s are integers. Algebraic "integers", a subset of algebraic numbers are roots of such polynomials where the coefficient of the highest power of x is 1, that is, they are roots of "monic" polynomials, such as, x - 7 would have the root 7, an integer.