To simplify \((19^4)^9\) using the Power Rule, which states that \((a^m)^n = a^{m \cdot n}\), you can multiply the exponents:
\[ (19^4)^9 = 19^{4 \cdot 9} \]
Now, calculate \(4 \cdot 9\):
\[ 4 \cdot 9 = 36 \]
So, the simplified expression is:
\[ (19^4)^9 = 19^{36} \]
Thus, the final answer is:
\[ \boxed{19^{36}} \]