After Dark at the Lagoon: Raccoons, Rats and Building Pests in Humboldt Park

A park laid out in 1869, a neighborhood built around it

Chicago annexed most of this land in 1869, the same year the West Park Commission laid out the park, one of three big West Side parks tied together by boulevards. It was named for the naturalist Alexander von Humboldt, whose statue went up in 1892. The stables were finished in 1895, and Jens Jensen, who worked from the stables' turret, later reworked the park in his prairie style, shaping the lagoon into a winding prairie river with naturalized edges. The boathouse on the water was completed in 1907. Today the park covers roughly 207 acres.

The neighborhood filled in fast. Land just outside the post-1871 fire limits allowed cheaper frame construction, streetcars reached North Avenue in 1895 and Pulaski Road in 1911, and Scandinavian, German, Jewish, Italian and Polish families built greystones on the boulevards and two-flats and cottages on the side streets. Puerto Rican, Mexican and African American families arrived after World War II. The 1966 Division Street riots and decades of disinvestment followed, then gentrification from the east beginning in the late 1990s.

For pests, two facts dominate. First, the park is a permanent wildlife reservoir with water, cover and food in the middle of dense housing. Second, most homes are more than a century old, with shared basements, rear wood porches and foundations that have been patched many times. One supplies the animals; the other supplies the openings. Most successful plans here deal with both at once.

The night shift: what leaves the park after dark

Raccoons den in the park's large trees, culverts and drainage structures, and around the lagoon's islands and banks. At dusk they leave and work the alleys along Humboldt Drive, North Avenue, Augusta, Division and the side streets for garbage, pet food and birdseed. Virginia opossums follow the same routes. Norway rats burrow along lagoon edges and under plantings and forage outward into yards. Gray and fox squirrels move from the park's canopy into parkway trees and onto roofs.

The pressure lasts all year but peaks twice. In late winter and spring, pregnant raccoons search for quiet, dry places to give birth, and the blocks within a few streets of the park get the first attempts. In fall, every animal is fattening up for winter and pushes harder into garbage carts and garages. Homes facing the park or the boulevards should assume visits will continue no matter what the neighbors do, and build defenses that last rather than reacting each season.

Raccoons in garages, chimneys and porch roofs

Raccoons are Humboldt Park's signature wildlife problem, and once a female chooses a den she is hard to discourage. Typical sites are detached garages with a gap where the roof meets the walls, unused chimneys on two-flats with no cap, the void above a rear porch ceiling, crawlspaces under rear additions and attics reached by tearing open a soffit or plastic roof vent. April and May are the worst months. Thumping overhead at dusk and dawn, chirring in a chimney, a torn vent or muddy prints on a downspout are the usual giveaways.

Illinois treats raccoons as protected furbearers with strict rules on trapping and relocation, and releasing one in the park is not allowed. Removal belongs with a licensed nuisance wildlife control operator. In spring, good practice is to confirm whether kits are present before excluding the mother. Many specialists use a one-way door or a timed eviction so the family leaves together, then repair the opening and install a stainless chimney cap or heavy-gauge screening. Trapping the mother alone often leaves orphaned kits in the wall, which creates a far worse problem a few days later.

Raccoon latrines on flat garage roofs and porch roofs, and droppings left in attic insulation, can carry roundworm eggs that are dangerous to people. Do not sweep or shovel them without protection. A wildlife specialist can remove contaminated insulation and disinfect the area after the animals are out, which also removes the scent that draws the next raccoon to the same spot.

Rats in the alleys between Division and North Avenue

Norway rats are the second big outdoor problem. Dense alleys, detached garages with cracked slabs and carts serving several units per lot keep food available, and the park, the rail embankments on the south and west edges and the occasional vacant lot offer burrowing ground. Look for burrows two to four inches across along garage foundations and fence lines, gnawed cart lids, smooth runways through grass and droppings near garbage. Homes that back onto the park or the rail lines usually see rats first, often in spring when colonies expand and young rats disperse to new burrows.

A rat problem here is rarely one yard's problem. The most effective approach combines tamper-resistant stations set along garages and fences by a licensed pro with physical fixes: replacing broken carts, sealing slab cracks, fitting heavy rubber sweeps on garage doors and clearing wood piles and debris. City 311 requests for alley baiting are worth filing alongside private service. Neighbors who coordinate on the same alley see far better results than one household working alone.

Mice, roaches and wet basements indoors

Indoors, house mice and German cockroaches are the pests residents mention most. Mice arrive in fall through foundation gaps, around gas lines and under rear doors, then settle into kitchen walls and basement storage. German cockroaches are mostly carried in on boxes, bags and secondhand appliances, then spread through shared walls and plumbing stacks in two-flats and three-flats. In buildings with leaky plumbing, the moisture supports oriental cockroaches in basements and house centipedes and silverfish in garden units.

Basements on the West Side flooded badly in the July 2, 2023 storm, when parts of the area and nearby suburbs recorded more than eight inches of rain. After any water event, pull out wet drywall, carpet and cardboard within a day or two and run fans and a dehumidifier. Damp debris feeds mold and gives cockroaches, centipedes and mice ideal cover. A plumber should look at a backwater valve or standpipe if the basement floods more than once; once it is dry, a pest provider can seal entry points and treat.

Greystone, two-flat or frame cottage

The boulevard greystones on Humboldt and Sacramento have Bedford limestone fronts over brick side and rear walls. The front rarely causes trouble. The weak points are at the back: eroded mortar at the foundation that lets mice and roaches into the basement, wood rear porches rebuilt several times that rot where they meet the masonry and draw carpenter ants, and the rear parapet and roof edge where raccoons and squirrels get in. Large parkway trees give both animals easy roof access.

West of the park, two-flats and three-flats with shared basements and rear stairs dominate. In those buildings, cockroach and mouse problems need every unit involved, because both pests travel the shared plumbing. Frame cottages are vulnerable at the sill plate and attic eaves, and many have crawlspaces under rear additions that opossums and skunks use. Toward the Belt Railway the yards get a little bigger, and the rail embankment becomes one more rodent corridor to watch.

Birds round out the exterior list. Rock pigeons roost on boulevard cornices, window hoods and the flat tops of bay windows, and their droppings collect on stoops and fill gutters. Sparrows and starlings wedge nests into gaps behind trim and into open dryer and bath vents. Low-profile spikes or netting on ledges, metal louvered vent covers and prompt cleanup of droppings with a mask and damp methods keep the problem manageable. Native songbirds are protected, so a provider checks the species before removing any nest.

Month by month near the lagoon

Wildlife near the park runs a little ahead of blocks farther from green space. Animals that winter in park trees and culverts start moving as soon as the ground thaws, and they reach the nearest garages first. Close openings in late winter, before birthing season makes removal slower, harder and more expensive. Blocks farther west toward the Belt Railway follow the same pattern a week or two later.

• February and March: raccoon and squirrel mating; males roam and test garage roofs and chimneys
• April and May: raccoon and squirrel births in attics, chimneys and garages, the most urgent removal season
• June to August: rats and roaches peak, mosquitoes breed near the lagoon edges, yellowjackets nest in porch voids
• July and August: heavy-storm season and basement flooding, followed by moisture insects
• September and October: animals push hard into garbage while fattening, and mice begin moving indoors
• November to January: mice and roaches dominate indoor calls, and opossums and raccoons ride out cold nights under porches

Hardening a home within a few blocks of the park

Because the park keeps resupplying animals, prevention here means hardening the building rather than reacting every season. These are the steps local providers recommend most often for greystones, two-flats and cottages near the park and boulevards. Roof and chimney items are best left to someone who works at height every day. Most of the ground-level items can be done in a weekend or two.

• Cap every chimney flue, including unused ones, with stainless steel
• Replace plastic roof vents with metal or screen them, and check soffits after windstorms
• Seal the gap where a garage roof meets its walls, and keep the overhead door closed at night
• Screen under rear porches and decks with hardware cloth buried at least six inches
• Keep garbage carts latched, and bring pet food and birdseed indoors
• Repoint foundation mortar and seal pipe entries with steel mesh
• Dry basements within 48 hours of any water and run a dehumidifier in summer

What a wildlife or pest visit involves

For an animal in the attic, chimney or garage, a licensed wildlife specialist starts with an inspection to find every entry point and confirm whether young are present, then sets a removal or exclusion plan that follows Illinois rules. Repairs and caps follow once the animals are out, and a raccoon job often takes several days to finish safely. An animal inside the living space usually gets a same-day response when a crew is available. For rats, mice and roaches, the technician walks the exterior and alley, then the basement and each unit, and may suggest coordinating with neighbors or other owners in the building.

Access drives cost and timing as much as the animal does. A greystone with a three-story rear wall may need tall ladders or a lift to reach the parapet. When you call, say whether the building is a single-family home, a two-flat or a condo, who controls the roof and garage, and whether you have heard young animals. Those details help a provider send the right crew and equipment the first time.