I cannot find Alfred in the 1920 or 1930 censuses, yet it's clear he lived until 1965.  He does appear to have been in the military, so was probably out of the country.

1.  LDS.  Family Search: Internet Genealogy Service: IGI - International Genealogical Index (online at FamilySearch.org).

William STRAUBE Spouse: Jessie Freemont HECKMAN Marriage: 02 Feb 1882, of USA Source: none given

Alfred Heckman STRAUBE Father: William STRAUBE; Mother: Jessie Freemont HECKMAN Source: none given

2.  1850 Census Every-Name-Index/Images (online at Ancestry.com):  Philip HECKMAN (æ 27, b. OH) and his wife, Sarah A. (æ 22, b. OH), are living in Morgan Co., OH (p. 305A).

3.  1860 Census Every-Name-Index/Images (online at Ancestry.com):  Jesse HECKMAN (æ 3, b. IL) is living in Kingston, DeKalb Co., IL (p. 90), with her parents, Philip HECKMAN (æ 37, b. OH) & Sarah A. (æ 30, b. OH), plus siblings.

4.  1870 Census Every-Name-Index/Images (online at Ancestry.com):  Jessie F. HECKMAN (æ 12, b. IL) is living in Kingston, DeKalb Co., IL (p. 443A), with her parents, Philip HECKMAN (æ 46, b. OH) & Sarah A. (æ 40, b. OH), plus siblings.

5a..  1880 Census Every-Name-Index/Images (online at Ancestry.com, Image #6 of 26):  Village of Kingston, [Kingston Twp.,] DeKalb Co., IL, Roll T9-0202, p. 100B, PN 6, SD 1, ED 32, enumerated 5 Jun 1880, official enumeration date 1 Jun 1880 (extracted by Diana Gale Matthiesen):¤•

1880:  for an explanation of the column headings, please see What the Numbers in the Federal Census Mean (missing columns contained no data).
1	2	3	4	5	6	8	9	13	24	25	26
55	58	Straub Wm	W	M	23		/	Hardware & Tin	IL	Ger	Ger
		______ Bertha	W	F	20	Sister	/	Keeps House	IL	Ger	Ger
		Hicks John	W	M	23		/	Tinsmith	"	"	"

5b.  1880 Census Every-Name-Index/Images (online at Ancestry.com):  Jessie HICKMAN (æ 22, b. IL/OH/OH) is living in Belvedere, Boone Co., IL (p. 357A), with her parents, Philip HICKMAN (æ 57, b. OH/PA/PA) & Sarah A. (æ 50, b. OH/PA/Eng), plus siblings.

6.  1890 Census:  the 1890 Census Population Schedules were destroyed.

7.  1900 Census Every-Name-Index/Images (online at Ancestry.com, Image #34 of 43):  144 [Unreadable], Downers Grove Village, Downers Grove Twp., DuPage Co., IL, Roll T623_298, p. 142B, SN 17, SD 2, ED 29, enumerated 13 Jun 1900, official enumeration date 1 Jun 1900 (extracted by Diana Gale Matthiesen):¤•

1900:  for an explanation of the column headings, please see What the Numbers in the Federal Census Mean (missing columns contained no data).
		1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	19	20	21	22	23	24	25	26	27
*	144	379	398	Straube William	Head	W	M	Sep 1857	42	M	17			IL	Ger	Ger	Manufacturer	0		Y	Y	Y	O	F	H
				_______ Jessie?	Wife	W	F	Sep 1857	42	M	17	1	1	IL	PA	OH				Y	Y	Y
				_______ Alfred	Son	W	M	May 1888	12	S				IL	IL	IL	At School		9	Y	Y	Y
*[indecipherable, but could be Fairmont]

8.  1910 Census Every-Name-Index/Images (online at Ancestry.com, Image #18 of 20):  144 Fairmont Avenue, Downers Grove Village (Ward 1), Downers Grove Twp., DuPage Co., IL, Roll T624_285 (Book 2), p. 97B, SN 11B, SD 48, ED 4, enumerated 22 Apr 1910, official enumeration date 15 Apr 1910 (extracted by Diana Gale Matthiesen):¤•

1910:  for an explanation of the column headings, please see What the Numbers in the Federal Census Mean (missing columns contained no data).
		1	2	3	4	5	6	7	8	9	10	11	12	13	14	17	18	19	20	23	24	25	26	27	28
*	144	174	182	Straube William	Head	M	W	49	M1	25			IL	Ger German	Ger German	Eng	Agent	Real Estate	OA	Y	Y		O	M	H
				_______ Jessie H	Wife	F	W	48	M1	25	1	1	IL	Ohio	Ohio	Eng	None			Y	Y
				_______ Alfred H	Son	M	W	21	S				MO	Illinois	Illinois	Eng	None			Y	Y	Y
*Fairmont Avenue

9.  1920 Census Every-Name-Index/Images (online at Ancestry.com):  can't find.

10.  1930 Census Every-Name-Index/Images (online at Ancestry.com, Image #14 of 33):  5256 Fairmont Ave., Village of Downers Grove, Downers Grove Twp., DuPage Co., IL, Roll 512 (Book 1), p. 78B, SN 7B, ED 22-22, SD 10, enumerated 12 Apr 1930, official enumeration date 1 Apr 1930 (extracted by Diana Gale Matthiesen):¤•

1930:  for an explanation of the column headings, please see What the Numbers in the Federal Census Mean (missing columns contained no data).
1	2	3	4	5	6	7	8	9	10	11	12	13	14	16	17	18	19	20	24	25
*	5256	174	177	Straube Jessie	Head	O	1200	R	N	F	W	72	Wd	N	Y	IL	IL	IL	Y	None
*Fairmont Ave

11.  SSDI:  Social Security Death Index (online at RootsWeb.com):

Name	Birth	Death	Last Residence	Last Benefit	SSN	Issued	Post-em
Alfred STRAUBE	21 May 1888	Aug 1965	60603 (Chicago, Cook, IL)	(none specfied)	359-14-5528	IL	No

12.  World War I Selective Service System Draft Registration Cards, 1917-18.  Microfilm Series M1509 (4277 rolls), National Archives and Records Administration, Washington, DC (card images and index online at Ancestry.com):

Microfilm Roll | Form | No:		1613183 | 3450 | 96
1	Name in full | Age in yrs:	Alfred H. Straube | 29
2	Home Address:	144 Fairmount Ave Downers Grove, Ill.
3	Date of Birth:	May 21 1888
4	Are you (1) a natural born citizen…	natural Born
5	Where were you born:	St. Louis Mo. U.S.A.
6	If not a citizen, of what country…
7	What is your present trade, occupation…	Reserve Officers Training Camp
8	By whom employed:	U.S.A.
	Where employed:	Ft. Sheridan, Ill.
9	Have you [dependents]?:	no
10	Married or Single | Race:	single | Caucasian
11	What military service have you had?
12	Do you claim exemption from draft?
Signature:		Alfred H. Straube
1	Height | Build:	Med | Slender
2	Color of Eyes | Color of Hair | Bald:	Blue | D. Brown | No
3	Physically Disabled:	No
Date of Registration:		June 5 1915
Draft Board:		Downers Grove, DuPage County, Illinois

Ft. Sheridan is in Lake Co., IL.  It is today called the "Ft. Sheridan Army Airfield" (SAAF).

13.  Paul Freeman.  Abandonded and Little-Known Airfields: Illinois, Northern Chicago Area:  includes a history of the airfield at Ft. Sheridan.

14.  Anon.  Oct 2005.  "A Grand Opening — The Straube Piano Company."  Flashback, Hammond Historical Society (Hammond, Lake Co., IN), v. MMV, n. 10, p. 3 (online at hammondindiana.com; article source said to be The Times newspaper, October 1904). 

I cannot reproduce the article due to copyright contraints, but the significant information for our purposes is that the Straube Piano Factory "faces Manila Avenue at the foot of Havanna Street," Hammond, IN, that it opened on 12 Oct 1904, that the company had been previously located in Downers Grove, IL, that the company President was James H. Broderick and its Secretary was E.R. Jacobson.

It appears William had sold the piano company after 1900, but before 1904, which explains why his occupation in 1910 is no longer "manufacturer."

.  Twentieth Century Time Capsule: Straube Piano Company — Dateline 1904 (online at www.hammondindiana.com).

.  Archives of the STRAUB Mailing List (online at RootsWeb.com).

.  Biographical Sketch of James F. JACOBSON (in the Archives of the INDIANA-L Mailing List; submitted Lora Radiches from an unknown source):

JAMES F. JACOBSON... was born in Chicago, February 5, 1885, son of Charles F. and Helena (Nicholson) Jacobson... [Their] three sons are Carl Herman Jacobson Thorby, Ernfrid R. and James F...  James F. Jacobson attended public schools in Chicago and after leaving school worked in a warehouse for two years, spent eight years with the Crerar-Adams Company, following which he and his brother, E.R. Jacobson, became associated in a music store at Indiana Harbor.  In 1914 they moved their business to Hammond, where the firm is the Straube Piano & Music Company, at 5247 Hohman Avenue.  It is one of the largest music merchandise houses in Northern Indiana.  James F. Jacobson is secretary and treasurer of the company, E.R. Jacobson is president, and C.H.J. Thorby is vice president.  Mr. James F. Jacobson is also secretary of the Straube Piano  Company, owning a piano factory at Hammond, which in normal times employs about 250 people.  The factory is at the corner of Manilla Avenue and Havanna  Street...

From what I've gathered, the retail showroom was on Hohman Avenue.  Another address I've come across is 252 Wildwood Road.  Interestingly, that address is now that of the American Conservatory of Music, part of the state university system, and other businesses.  Checking a map, Wildwood intersects with Hohman Avenue.

.  [A History of] Centier Bank (online at www.indianahisotry.org):

Centier Bank Founded: 1895 Location... Whiting... Henry Schrage, the organizer of Centier Bank, was a founder of the city of Whiting... Henry Schrage's son Walter... became president... Walter suffered a stroke at the bank on 9 October 1941 and died that evening.  His son Walter, Jr., who had worked at the bank as a clerk from 1931 to 1938 before leaving to manage the family-owned Straube Piano Company in East Chicago, returned to succeed his father as president.

.  C.G. Conn (online at libraryoflibrary.com)

C.G. Conn Ltd., sometimes called Conn Instruments or commonly just Conn, was a United States manufacturer of musical instruments... From 1940 to 1950 they owned the Haddorff Piano Company, and from 1941-2 the Straube Piano Company...

.  WorldConnect / Ancestry World Trees (online at RootsWeb.com/Ancestry.com).