I visited both components of this WHS in 2023 by rental car from Arica. It is a long drive in the Atacama desert in Northern Chile which I'll gladly revisit next time using Antofagasta or San Pedro de Atacama as my base (even if it might not include anything WH related).

I started with the larger and main component of this WHS, Humberstone Saltpeter Works. There is a handmade WHS plaque in each of the two components as well as a more formal/official one at both. Combined tickets can be bought at any one of the two components and there is enough space to park in front of both sites. Although both components are very close to each other by car (small unpaved road towards the last stretch to Santa Laura), a long walk between them is better avoided as it is a very dusty trail with no shade whatsoever. If you don't have a rental car, I would suggest hitching a ride from any other tourists visiting Humberstone. It's true that you can spend a full day to thoroughly visit both components, but if you read up and do your research online on the highlights you wouldn't like to miss, a packed and moderately active half day could be enough to try to grasp the site's OUV, or at least whatever is left of it.

Humberstone and Santa Laura Saltpeter Works are testament to the historical importance of saltpeter mining in Chile and the culture and social agenda that developed around it in the late 19th century. Other non-inscribed "nitrate" towns related to saltpeter mining in the area are Chacabuco, Maria Elena, Pedro de Valdivia, Puelma and Aguas Santas. Both Humberstone and Santa Laura Saltpeter Works nowadays look like abandoned ghost towns and although their derelict buildings have been removed from the list of WHS in Danger in 2019, I really can't imagine how these components could have been worse off.

In Humberstone, the area to cover is much larger and there is much more left to see here than in Santa Laura. Humberstone includes a residential area with a church, a theatre, a school, a grocer, a cooling chamber, living quarters, guest houses, a swimming pool (later reused in the industrial process). Although there are a number of signs and information boards in English and in Spanish, I recommend taking a photo of the map drawn near the Humberstone entrance ticket booth to be able to locate the area where you might have possibly missed visiting. Even though the residential area has been recently restored, there are still some buildings which have collapsed or need restoration works again. The more industrial area of Humberstone is much more derelict and the main elements here are rusty machinery, rusty industrial tools, rusty railways, locomotives and wagons, rusty structures, and more rust, rust and rust. The wind reigns supreme here and is constantly leaving its heavy toll on any remaining saltpeter mining structures. I enjoyed following and learning about the industrial process first hand from the remains here. In the industrial area, there are signs that you enter what's left of the structures at your own risk and rightly so, as every day the security guards at site, patrol the area before opening and closing the sites, to clear some new area which has crumbled or been blown off by the wind. You also have to watch your step wherever you walk as there are sharp rusty remains, barbed wire, nails, etc. everywhere making it quite easy to injure yourself if you're not extra careful.

The Santa Laura Saltpeter Works is much smaller and the industrial giant has recently lost a number of its "iconic" components which might be restored/reconstructed in the near future, namely one of the tall chimneys which was being secured during my visit, and the conveyer belt which has collapsed and broken down in 2 separate parts. Make sure to bring good sturdy shoes, water and a cap here as you're literally roaming in the desert heat, which is exacerbated by the constant winds.

Overall, this industrial WHS deserves its place on the WH list, but it is also a very good example of how several industrial WHS inscribed on the list risk disappearing due to the passage of time and their harsh natural environments. They aurely won't be around for as long as the Roman, Egyptian or Medieval WHS, but perhaps that might be a good thing after all!