The modern **acoustic guitar**, as we know it today, evolved over centuries, but its most significant development came in the **19th century** thanks to **Antonio de Torres Jurado** (1817–1892), a Spanish luthier often called the “father of the modern classical guitar.”

### **Key Contributions of Antonio de Torres:**
1. **Larger Body Design** – Torres increased the guitar’s size and refined its shape, improving volume and tone.
2. **Fan Bracing Pattern** – He developed an advanced fan-style bracing system inside the guitar, which strengthened the soundboard while allowing better resonance.
3. **Standardized Scale Length** – He established a scale length (string length from nut to bridge) of about **650 mm**, which became the standard for classical guitars.

While Torres focused on **classical guitars**, his innovations influenced all modern acoustic guitars, including **steel-string acoustics**, which became popular in the early 20th century.

### **Later Developments:**
– **Christian Frederick Martin** (1796–1867) and his company, **C.F. Martin & Company**, adapted Torres’ designs for **steel-string guitars** in the U.S., leading to the modern **flat-top acoustic guitar** (used in folk, country, and pop music).
– **Orville Gibson** (1856–1918) and the **Gibson Company** later introduced archtop guitars, further diversifying acoustic guitar designs.

So, while no single person “invented” the modern acoustic guitar, **Antonio de Torres** laid the foundation, and luthiers like **Martin and Gibson** refined it into the instruments we know today.