The San Miguel volcano, in eastern El Salvador, is one of (if not the) most active volcanoes in El Salvador. At 2130m, it is not the tallest (falling behind Volcàn Santa Ana and Volcàn San Vicente) but it is probably the fiercest-looking, rising straight up from the surrounding lowlands almost 2000 meters, with a barren summit and occasional plumes rising from the half-mile-wide crater. It is readily visible anywhere in the eastern parts of El Salvador, and even from parts of Honduras and Nicaragua.
This volcano, like many in Central America and El Salvador specifically, is not protected by any kind of National Park. It simply is there, for anyone to climb who cares to get the necessary permissions and do the work. It is a steep scramble, as there are no trails and takes several hours for a round-trip at best. This area is also known for a lot of bandits on the volcano, so taking security in the form of police or soldiers is a must.
Getting ThereThe volcano, like Chichontepec, can be climbed from multiple sides, but perhaps the easiest way to climb it is to go from the west. It is also necessary (in my opinion) to be a Spanish-speaker to be able to set up the guide, get an escort, etc. The town of San Jorge is where I was able to get guiding set up when I climbed it as a Peace Corps volunteer. There is a Proteccion Civil office there who knows the local police, etc. and can arrange for a trip to the top. When I went, we arrived ~9am, and were on our way up the volcano by 11. Not bad...
From San Jorge, we approached the volcano's northwest flank, to a HUGE coffee finca, (roads visible in Google Maps) where we solicited permission of the owner to go up through his plantation as high as the road went. With our 4x4, and a guide from the finca, we were able to climb to the elevation of about 1200m, leaving only 1000m or so to climb. From there, despite being promised it was "only 20 minutes" it took a few hours to climb, and about 1 hour to descend. We had a police officer and two soldiers with us, and that was pretty common.
I am sure that the volcano can be climbed from other directions, but this way was the best for us, and seemingly one of the most direct ways, owing to how high the road went in the coffee finca. Feel free to explore other ways though, especially trying to contact guides from San Miguel, who surely know more about it than me.