Twin Branch — the dam, the Power City, and the neighborhood

1903 – the hydro plant still generating in 2026

The dam: The Twin Branch Dam stands on the St. Joseph River at the east side of Mishawaka, where Twin Branch Creek comes down to the river just above it — the creek gave the dam, the plant, and in time a whole neighborhood their name. The dam's reference profile records that it was first called the Hen Island Dam, for the islands below it, both of which the river had taken by the 1950s, and that an 1835 dam attempt by the St. Joseph Iron Works near the site precedes it; the iron-works dam and race of the 1830s are the Story of Mishawaka section's record and are cross-referenced, not retold. The modern dam was built by Sanderson & Porter of New York for the St. Joseph and Elkhart Power Company — the company commissioned the dam on 26 February 1900, in the profile's account — and power was first produced on 16 December 1903. It is the tallest dam with a hydroelectric station on the St. Joseph River in Indiana. The National Inventory of Dams (IN03011) gives its measure: a gravity dam of timber-crib and earth construction, 41 feet high and 946 feet long, holding 10,000 acre-feet, built 1903, owned by the Indiana & Michigan Power Company.

The ownership course: In 1904 Charles A. Chapin purchased, for over $1,000,000, the interest the South Bend Electric Company held in the dam. In 1907 the St. Joseph and Elkhart Power Company merged with the Indiana & Michigan company, and the dam's profile carries that it "has been owned and operated by American Electric Power / Indiana Michigan Power since 1922" — printed at the profile's strength, the corporate chain between the 1907 merger and the modern I&M not separately documented. The generating figures conflict and are printed whole: one carried figure gives the dam as "capable of producing 2,600 kilowatts," while another records that "in 1957, the dam only generated 7,200 kilowatts." Neither figure is an I&M-published rating reached, and they are not reconciled here; the company's own current account, below, counts the river's six plants together.

The Power City: The dam was only half the works. On the north bank stood the steam generating station — a huge complex, in the account of Peter De Kever's Lost Mishawaka, whose chapter on the works is titled "When Mishawaka was the Power City: The Story of the Twin Branch Dam and Power Plant," that "once powered the entire city of Mishawaka and beyond" and is now gone. The station was in service by 1927, when the Twin Branch Railroad was organized to feed it: a line of under two miles hauling coal from a connection with the New York Central's Elkhart & Western to the generating station on the river, worked first by two steam locomotives, then in the 1930s by storage-battery locomotives, with pantographs and catenary added during the Second World War to cut battery-charging time. The steam station shut down in June 1978, and the little railroad was abandoned with it, in the Monon Society's history of the line; one of its locomotives survives at the Indiana Transportation Museum. The neighborhood east of the dam took the plant's name outright: Twin Branch is east Mishawaka's own name for itself, the creek's word by way of the power works.

The present state, November 2026: The hydro plant never stopped. Indiana Michigan Power's own account of its hydro fleet (26 March 2024) counts six hydroelectric plants on the St. Joseph River generating more than 22 megawatts together — power for about 15,000 homes — and names Twin Branch, commissioned 1903 in Mishawaka, the oldest hydro facility in the American Electric Power fleet. The name has also gone up the hill: the Twin Branch Solar Power Plant, I&M's 2.6-megawatt array just east of Mishawaka in the industrial ground north of the AM General factory, went online on 18 August 2016, expected to power about 365 homes a year. And the hydro fleet's future is an open public question as this section is written: I&M is seeking public input on the future of its hydro facilities, Twin Branch among them, with an open house set for 12 November 2026 at the Ironworks Event Center in Mishawaka — the company having determined, after similar Indiana hearings the year before, that hydro remains cost-effective with local support, and moving to seek renewal of the plants' licenses.

Sources:

1. National Inventory of Dams, IN03011 (Twin Branch Dam) — gravity timber-crib and earth construction, 41 feet high, 946 feet long, 10,000 acre-feet of storage, built 1903, owner Indiana & Michigan Power Company; and the dam's reference profile — the Hen Island Dam first name, Twin Branch Creek above the dam, the 1835 Iron Works dam attempt near the site, Sanderson & Porter's construction for the St. Joseph and Elkhart Power Company (commissioned 26 February 1900), first power 16 December 1903, the tallest dam with a hydroelectric station on the St. Joseph River in Indiana, Chapin's 1904 purchase at over $1,000,000, the 1907 merger, the AEP/I&M ownership from 1922, and the two generating figures, 2,600 kilowatts of capability and 7,200 kilowatts in 1957, printed as they stand.
2. Monon Society, "Twin Branch Railroad" — the railroad organized in 1927, under two miles, hauling coal to Indiana & Michigan Power's generating station on the St. Joseph River on Mishawaka's east side; the New York Central Elkhart & Western connection; the steam, battery, and catenary course; and the line's abandonment in June 1978 when the generating station was shut down and closed.
3. Peter J. De Kever, Lost Mishawaka, the Twin Branch chapter, as discussed with the Mishawaka Historical Museum (Round the Bend podcast account) — "When Mishawaka was the Power City"; the massive north-bank steam-plant complex that once powered the entire city and beyond, now gone.
4. Indiana Michigan Power, the company's hydroelectric account (26 March 2024) — six hydro plants on the St. Joseph River at more than 22 megawatts combined, about 15,000 homes; Twin Branch the oldest hydro facility in the AEP fleet, commissioned 1903 at Mishawaka; and I&M's Twin Branch solar release via Moody on the Market (18 August 2016) — the 2.6-megawatt plant online, just east of Mishawaka, north of the AM General factory.
5. Moody on the Market (10 November 2026) — I&M's public-input process on the future of its hydro facilities including Twin Branch, the open house of 12 November 2026 at the Ironworks Event Center, Mishawaka, and the company's license-renewal course after the prior year's Indiana hearings.