History of MTA Maryland (Wikipedia)
In 2017, MTA completely overhauled its bus network. Including a central core of bus routes now identified with colors. The result is a bus system bearing little resemblance to that which evolved from the former streetcar network. Thus no attempt is made to compare historic routes with the new routes. But the above Wikipedia link attempts to make these associations.
Discontinued routes are in parentheses. Newer and many short lived routes are not listed.
Bus routes were originally lettered, many of them feeder routes. Bus routes were later assigned available higher numbers, or were consolidated to become extensions or variations of what historically were streetcar routes.
Route Former Route Streetcars Trolley Motor Route Number Numbers Name Introduced Bus Bus Discontinued (0) Druid Hill Ave. 1897 4/24/20 to #5 1 Fulton Ave. 1895 8/ 1/48 6/21/59 1 2 Carey St.-Fort Ave. 1893 12/13/48 6/21/59 (2) Carey St.-Fort Ave. 1893 12/13/48 6/20/59 to #1 (2) 8 Frederick Rd.-Catonsville 1895 11/ 3/63 2000's to #10 (3) Linden Ave. 1893 11/15/36 3 Loch Raven Blvd.-Baynesville 1893 6/22/47 (3) Q 12 Wilkens Ave.-Halethorpe 1893 12/15/35 6/20/87 to #31 (4) Edmondson Ave.-Windsor Hills 1894 9/17/54 to #15 (4) Monument St. 1894 12/30/35 to #6 4 East Point-Dundalk 11/15/71 5 0 27 Druid Hill Ave.-Park Heights Ave. 1892 6/27/48 5 Cedonia 12/ 3/05 1/ 1/39 6/23/57 (6) 29 Roland Park-Boulevard 10/ 8/08 6/22/47 6/14/77 to #61 (6) 4 Monument St. 1894 3/21/48 6/14/77 to #62 (6) Curtis Bay 1892 3/21/48 6/14/77 to #64 (7) Govanstown-Irvington 1893 1/ 4/31 7 18 Reisterstown-Canton 1894 6/ 8/52 8 Greenmount Ave.-Towson 1895 11/ 3/63 (8) Frederick Rd.-Catonsville 1895 11/ 3/63 6/19/82 to #2 (9) Wilkens Ave.-Halethorpe 1893 11/30/26 to #3 (9) Ellicott City 12/ 1/27 6/20/55 2/ 1/57 9 Hunt Valley 6/16/74 (10) Howard St.-Roland Park 1893 4/14/40 6/21/59 9/ 4/82 to #27 (10) 25 Falls Rd.-Pimlico 1897 4/24/49 9/ 4/82 to #27 10 Eastern Ave.-Sparrows Point 1893 4/14/40 6/21/59 10 8 2 Frederick Rd.-Catonsville 1895 11/ 3/63 11 A Charles St.-Dunkirk 7/26/15 11 27 Washington St.-Lansdowne 12/ 3/05 1/ 1/39 6/23/57 (12) John St. 1893 12/ 1/38 (12) Westport 10/ 1/18 12/31/38 to #17 13 North Ave. 1890 1/10/54 13 33 Milton Ave. 2/28/50 (14) Edmondson-Ellicott City 1898 9/17/54 to #23 14 Annapolis-Baltimore 4/29/73 15 Gay St.-Belair Rd. 1899 11/ 3/63 (15) Baltimore St. 1899 5/ 8/48 to #20 15 4 Edmondson Ave.-Windsor Hills 1894 11/ 3/63 15 35 Walrook-Lorraine 1/ 1/04 2/28/54 (16) Madison Ave.-Broadway 1893 5/ 9/48 1/ 9/59 (17) St. Paul St.-Loch Raven Blvd. 1893 6/21/47 to # 3 (17) 12 Russell St.-Westport 10/ 1/18 6/21/47 to #28 (18) Pennsylvania Ave.-Canton 1894 6/ 8/52 9/ 5/59 to # 7 19 Harford Rd. 1894 6/17/56 (19) 31 Garrison Blvd. 6/10/17 6/17/56 6/20/87 to #91 (20) Orleans St. 1894 11/23/29 20 15 N Baltimore St. 1899 1/16/32 21 Preston St.-Caroline St. 1895 3/ 6/38 6/23/57 (22) Washington St.-Canton 1898 6/23/38 22 S Crosstown 5/23/37 22 34 Highlandtown 5/23/07 3/ 5/50 23 P Eastern Ave.-Middle River 1897 6/ 2/33 23 14 Edmondson-Ellicott City 1898 9/19/54 (24) Sparrows Point 5/ 2/03 1926 to #26 (24) 28 Lakeside 10/17/24 1/28/50 24 Tidewater Village-Franklin Sq. 1/31/88 (25) Falls Rd. 1897 4/24/49 6/20/59 to #10 (26) 24 Sparrows Point 5/ 2/03 8/31/58 6/20/59 to #10 (26) Providence 11/24/76 8/28/97 (27) Preston St. 12/ 3/05 1/ 1/39 6/23/57 9/ 5/59 to # 5 (27) Washington St.-Lansdowne 12/ 3/05 1/ 1/39 6/23/57 9/ 5/59 to #11 27 25 10 Howard St.-Falls Rd. 1893 4/14/40 6/21/59 (28) Lakeside 8/24/24 11/23/29 to #24 (28) 12 17 Russell St.-Westport 10/ 1/18 6/22/47 8/26/01 (28) 32 Liberty Heights Ave. 4/25/20 9/ 4/55 8/26/01 (29) Roland Park-Boulevard 10/ 8/08 6/22/47 1/10/59 to #6 (30) Fremont Ave. 1894 3/25/50 8/22/58 1/31/92 (31) Garrison Blvd. 6/10/17 10/12/52 to #19 31 12 3 Wilkens Ave.-Halethorpe 1893 12/15/35 (32) Liberty Heights Ave. 4/25/20 9/ 4/55 1/10/59 to #28 (33) West Arlington-Patterson Park 11/14/20 6/26/48 (33) Milton Ave. 2/28/50 9/ 4/54 to #13 33 Coldspring Lane 1/17/77 (34) Highlandtown 5/23/07 3/ 5/50 6/19/75 to #22 (35) Walrook-Lorraine 1/ 1/04 2/28/54 1/29/66 to #15 35 Philadelphia Rd. 5/ 1/70 36 Alameda 6/22/47 (37) Cherry Hill 6/22/47 6/15/74 (40) M Glyndon 7/ 3/32 9/22/51 to #5 44 Belvedere Ave. 7/ 7/46 (45) Loch Raven Blvd.-Baynesville 3/13/49 9/ 1/56 to #3 (46) Union Ave. 4/20/01 4/24/49 4/27/70 (47) Key Ave. 1899 9/14/50 1/29/66 to #5 50 U Mannasota Loop 6/30/40 51 D Hilton St.-Bentalou St. 6/ 1/23 (52) J Lansdowne-Morrell Park 7/ 7/27 6/22/57 to #27 (53) R Carney-Parkville 10/ 4/36 9/ 1/56 to #19 (54) E Randallstown-Gwynn Oak Jct. 2/22/31 9/ 3/55 to #32 (55) H North Point Rd. 4/ 1/25 10/18/52 55 Taylor Ave. 4/29/73 (56) Murray Hill 8/ 1/48 4/18/53 to #11 (57) Gorsuch Ave. 6/22/47 6/21/75 to #22 (58) Brighton 6/27/48 9/15/51 to #47 (58) Brighton-Greenspring Manor 8/10/52 1/27/73 to #44 61 Roland Park 6/19/77 (63) X Pennington Ave. 1/ 1/46 1951 to #6 64 Light Street-Brooklyn 6/19/77 Route Former Route Streetcars Trolley Motor Route Number Numbers Name Introduced Bus Bus Discontinued (A) Charles St. 7/26/15 6/21/47 to #11 (B) Mount Royal Ave. 7/15/22 6/21/47 to #28 (C) The Alameda 3/ 1/24 1/30/43 (D) Bentalou St. 6/ 1/23 10/ 2/48 to #51 (E) Randallstown 2/22/31 6/26/48 to #54 (F) Chester St. 6/16/24 1950 to #33 (G) East Fayette St. 4/ 1/25 8/ /49 to #17 (H) North Point Rd. 4/ 1/25 1950 to #55 (I) Monroe St. 7/25/25 11/26/38 to D (I) Dolfield Ave. 5/12/40 6/26/48 to #51 (J) Lansdowne 7/ 7/27 1948 to #52 (K) Hollins Ferry-Lakeland 12/ 5/27 6/21/47 to #28 (L) Reistertown Rd. 7/ 3/29 6/26/48 to # 7 (M) Glyndon 7/ 3/32 6/26/48 to #40 (N) West Baltimore St. 1/16/32 5/ 8/48 to #20 (O) Homeland 4/ 1/31 6/21/47 to #11 (P) 23 Eastern Ave.-Middle River 1897 6/ 2/33 1/21/50 to #23 (Q) 9 3 Wilkens Ave.-Halethorpe 1893 12/15/35 5/ 8/48 to #12 (R) Carney 10/ 4/36 1948 to #53 (S) Crosstown 5/23/37 6/21/47 to #22 (T) Northwood 1/ 1/40 6/21/47 to #3 (U) Mannasota 6/30/40 12/18/48 to #50 (V) Armistead Gardens 6/15/41 3/20/48 to #6 (W) Westinghouse 12/28/42 10/20/45 to J (X) Pennington Ave. 1/ 1/46 1950 to #63 Route Former Route Streetcars Trolley Motor Route Number Numbers Name Introduced Bus Bus DiscontinuedThe Wilkens Ave.-Halethorpe segment was introduced in 1893 as part of streetcar route #9, 11/30/26 to route #3, 12/15/35 to bus route Q, 5/ 8/48 to route #12, 9/ 5/59 to # 3, 6/20/87 to route #31.
The Eastern Ave.-Middle River segment was introduced in 1893 as part of streetcar route #23, 6/ 2/33 introduced bus extension route P, 2/10/42 streetcar segment to bus route P, 1/22/50 back to route #23.