Most Iowans Are Not Aware of This Secret Tunnel

Tunnel systems, such as the Anton Anderson Memorial Tunnel in Alaska, are ideal for moving people under large rivers or over snow-covered mountains. Iowa doesn’t have high mountains that must be blasted through to save travel time and risk.

Iowa also lacks big rivers that commercial traffic must cross, thus bridges are a better option. So, where is Iowa’s longest tunnel?

Take a look at where this tunnel is, how it was created, and more. People who dislike small places will greatly benefit from avoiding this tunnel!

What is Iowa’s Longest Tunnel?

The Harmon Tunnel is Iowa’s longest tunnel, spanning around 150 feet long, 40 feet wide, and 15 feet high. This tunnel, which runs beneath the ridge through which the route was built, can accommodate two-way traffic.

The tunnel’s interior allows for walking on either side. That way, visitors to Pammel State Park can travel through the tunnel and continue hiking or riding.

Most Iowans Are Not Aware of This Secret Tunnel

So Iowa’s longest tunnel is quite tiny in comparison to some of the longest tunnels in the United States. The tunnel has a fascinating history, despite its modest length. First, let’s figure out where to find this structure.

Where is Harmon Tunnel Located?

Harmon Tunnel is situated in Pammel State Park in Madison County. That puts it around four miles southwest of the nearby city of Winterset. People travel from all around the state to go camping, stay in yurt cabins, and trek around the area.

The Harmon Tunnel is the only highway tunnel in the entire state. The tunnels road is called Pammel Park Road, and it connects to IA 322 when moving west to east. After passing through the tunnel, IA 322 continues north to IA 92.

The tunnel passes through a limestone ridge. The ground above the tunnel is not completely level, and a notice on the tunnel’s façade cautions about falling pebbles. Furthermore, the Middle River flows extremely close to the tunnel, making it impassable when the water level rises too high. These hazards are caused by the structure’s location and construction methods.

At first appearance, one could assume that the tunnel was built in the middle of nowhere. They’re correct. However, the tunnel was not built to handle cars. When we analyze the tunnel’s history, we may understand why it was built at this location.

Read More: Claustrophobic People Must Avoid This Nebraska’s Longest Tunnel

When was Iowa’s Longest Tunnel Built?

Iowa’s longest tunnel was initially constructed in 1858. Originally, a man called William Harmon and his three sons dug the tunnel. Their goal was to break through the soft black shale of the ridge and connect their sawmill to the Middle River. That way, they could use the water to run the mill.

We don’t know how long it took the four guys to excavate the claimed 150 feet through the crest. Eventually, they finished the millrace. However, the millrace they dug was not as large as the tunnel today.

So 1858 would not be the last time the tunnel people changed the tunnel. The Harmon sawmill will eventually become a grist mill. In 1904, the idea of a mill was finally abandoned.

In the early 1900s, various Iowa roadworks organizations recognized the tunnel’s potential and began the process of enlarging it. In 1925, Harmon Tunnel became the state’s first and only highway tunnel. Only three years later, Pammel State Park opened.

However, the tunnel’s construction did not end there. In addition, the tunnel was expanded or fortified in 1982. Nowadays, the tunnel is broad enough to accommodate two lanes of traffic and a sidewalk on either side.

However, the tunnel is barely 15 feet tall at its highest point. This means that automobiles, vans, SUVs, and compact passenger vehicles will fit, but nothing else.

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