1870 Census: Mt. Pulaski, Logan Co., IL - page
next door to his mother Elizabeth. and brother Henry:
#76 Mayer, George 29? IL Keeps Saloon [John & Elizabeth's son]
Katie? (actually looks like Katre) PA - Probably short for Katherine

#77 Mayer, Elizabeth, 53 PA - Page
Jacob 30? IL Harness maker
Henry 25 IL Saloon Keeper
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1880 Census - Mt. Pulaski, Logan Co., IL - Page 188
#442 Mayer, Jacob 30 IL Ger Ger Harness Maker
Mary 27 IL Ger Ger
Walter 5
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Same as above with more detail.
Census Place: Mt. Pulaski, Logan, Illinois
Source: FHL Film 1254227 National Archives Film T9-0227 Page 188C

Jacob MAYER Self M M W 30 IL [born 1850]
Occ: Harness Maker Fa: GERMANY Mo: GERMANY
Mary MAYER Wife F M W 27 IL
Occ: Housekeeper Fa: GERMANY Mo: GERMANY
Walter MAYER Son M S W 5 IL
Fa: IL Mo: IL

Logan County, Illinois
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FOX, LAMB, LEE, MATTFELDT, MAYER, RIDGELEY, SCHICK, WORK
History of Logan County - Mt. Pulaski Section - Published in 1886, Chicago Interstate Publishing; Chicago, page 796

J. Mayer & Brother, harness makers, of Mount Pulaski. John W. and Jacob Mayer, are sons of the late John G. Mayer, who was born Feb 25, 1809, in Wurtemburg. Coming to America in 1832, he spent four years in Lancaster County, Pennsylvania and in 1836 married Elizabeth Work, born in that county, October 21, 1812. Moving then to Springfield, he was employed in LAMB'S Foundry, and later in RIDGELEY'S bank as porter. At one time the brothers, George, John and Michael MAYER, each owned and ran a dray in Springfield. In 1846 John G. Mayer removed his family to a new farm in Mount Pulaski Township, where he lived until 1850. He then went into mercantile business with his brother George Mayer, continuing with him until 1859, when on account of failing health, he removed from the business and returned to the farm where he died April 1, 1866 after 9 years of almost constant battling with disease. His widow now resides in Mount Pulaski. There were seven children born to them -- Samuel, born October 22, 1837; Magdalena, born February 13, 1839; George, born May 16, 1840; Anna, born January 4, 1844; John W., born August 1, 1846; Jacob, born March 16 1850; and Henry, born June 18, 1854. Magdalena Mayer married Henry FOX and died at Dwight Illinois, October 10, 1879. The five now living are all in Mount Pulaski and vicinity. Samuel Mayer married Mary W. LEE, September 15, 1862, in Lincoln, Illinois. Of the seven children born to them four are living -- Annie E., born November 21, 1863; George A., born July 19, 1867; Mary C., born August 17, 1870; Stella L., born April 3, 1876; Sarah O., born March 13 1866 died November 24, 1871; Ida B., born June 5, 1869, died March 24, 1876; Henry L., October 2, 1872, died August 6, 1873. John W. Mayer married Mary MATTFELDT, of Michigan. Of the four children born to them, three are living-- Harmon, Oscar and Clarence. Freddie died aged two years. They were all born in Mount Pulaski. Mr. Mayer began the saddlery and harness business in Mount Pulaski in 1866, forming a partnership with his brother Jacob in 1872. Both brothers cast their votes for the Democratic party. Jacob Mayer was married November 7, 1872, to Mary SCHICK, born in Mount Pulaski, August 15, 1853. They have 2 children-William Walter, born July 22, 1875 and Elmer B., born June 1, 1881, both born in Mount Pulaski. Mr. Mayer and family are members of the Lutheran church. The Mayer Brothers are well known among stockmen as owners of the magnificent stallion, King o' the Lyons, a thoroughbred, Clydesdale horse, registered in the Scotch Clydesdale stud-book, as 1461, and in the American Clydesdale stud-book (volume 2), as 1251. He was imported in 1881 by HUSTON Brothers, and purchased by J. Mayer & Brother in March, 1883. The horse is in color a deep, rich blood bay, with black legs, mane and tail, and weighs 2,050 pounds. He is seventeen and one-half hands high, and has taken 2 sweepstakes premiums at the Logan County Fair, one in a ring of twenty-one horses. His sire was Lord Lyon, No. 489, dam Flora, No. 59, she by Victor, No. 892, and has a registered pedigree extending back seventy-five years. He is beyond question the best horse of his class in Logan County. General Garnet is another imported Clydesdale horse, No.2121, in volume 5, Scotch Clydesdale stud-book, and 1238 in volume 2, of the American stud-book. He was sired by Topsman, No. 886, dam Jean, No, 645, she by Robin, No. 703. He is a beautiful and extremely docile animal. He took the first prize in the ring of imported three-years-olds at the Logan County Fair, in 1884. He was imported by HUSTON Brothers in March, 1883, and purchased by the Mayer Brothers in December of the same year. These gentlemen have won an enviable reputation among the horsemen of this section and their horses are recognized as among the first-class stock animals in Central Illinois.
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Transcriber's note: This is the only reference, I've found, that lists 3 Mayer brothers:
George, John and Michael MAYER. Previously I've only seen George and John G.
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Logan County, Illinois
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MAYER, REITZ, SCHICK, STOLL, WORK
Biographical Record of Logan County, published in 1901 Chicago: S.J. Clarke Publishing Co., Page 460.
JACOB MAYER

Among the leading business men and prominent citizens of Mt. Pulaski is numbered Jacob Mayer, of the well-known firm of J. Mayer & Brother, manufacturers of harness and dealer in buggies. He was born in that village on the 16th of March 1850, and is the son of John G. and Elizabeth (Work) Mayer. The father was born in Wuerttemberg, Germany, in 1808, and in 1832 crossed the broad Atlantic and first located in Philadelphia, Pennsylvania. On coming west, he located in Springfield, Illinois, where he was employed in a general way in the Ridgley Bank until 1848 when he removed to Logan county and settled on a farm in Mt. Pulaski township, where he spent two years. In 1850 he took up his residence in Mt. Pulaski, where he was engaged in General Merchandising with his brother George under the firm name of Mayer Brothers for tem years. He then followed farming in Mt. Pulaski township until his death, which occurred in 1865. He there owned two hundred and forty acres of rich and arable land, and had three hundred and ten acres elsewhere. His wife who long survived him, passed away in March, 1895. She was born in Strassburg, Lancaster county, Pennsylvania in 1813. They had a family of seven children, five sons and two daughters, namely: Samuel; Martha; George; Anna, wife of E. Stoll who died September 27, 1901; John W.; Jacob; and Henry, deceased.

Jacob Mayer was educated in the public schools, which he attended until fifteen years of age, and during the following three years was with the family on the farm. He then learned the harnessmaker's trade with the firm of Mayer and Reitz, serving a three years' apprenticeship. In October, 1871, he purchased the business, and carried it on alone until 1873, when he admitted his brother John W. to partnership, the firm became known as J. Mayer and brother. They have built up and excellent trade and have occupied the same building since December, 1873. Besides his business property our subject owns a nice home in Mt. Pulaski, which was purchased by him in 1888, and he also has a good farm of one hundred and sixty acres in Kansas. He is a wide-awake, energetic businessman, and generally carries forward to successful completion whatever he undertakes.

In 1872 Mr. Mayer wedded Miss Mary Schick, of Mt. Pulaski, a daughter of Adam and Lena Schick. They have two sons: William W., a jeweler of this city; and Elmer B., who is attending the State University at Champaign, Illinois. The family is one of prominence in the community where they reside and have a host of friends throughout the county. Mr. Mayer is a member of the Lutheran church and has taken an active part in local affairs, having served a number of terms on the city council and is at present a member of the board of education. He is rather liberal in his political views and is now a stanch Sound-Money Democrat.